First pterosaur tracks from Brazil

Abstract

We describe here the first record of pterosaur fossil tracks from the Lower Cretaceous of Brazil, based on new records from the Botucatu Formation (Paraná Basin). These rocks comprise a desert region of dunes and interdunes from which several tetrapod tracks/trackways are known, including tridactyl dinosaurs, lizards and small mammals; giving some clues about the inhabitants of this ancient desert. The new findings were recovered from the well-known Ouro ichnosite (Araraquara Municipality, São Paulo State), and are represented by isolated and well-preserved tridactyl tracks, with left manus (LPP-IC-0232) being digitigrade and the left pes (LPP-IC-0233) being plantigrade. The manus imprint is asymmetrical with a long impression of digit III pointing backwards; these features distinguish this track from tridactyl dinosaurs, resembling a rhombic track morphology, diagnostic of <italic>Pteraichnus</italic>. Furthermore, in the pes imprint, the metatarsal region is about four times longer than the digital region. Three short, anteriorly directed digit impressions are present, in addition to the midfoot arch (pedal isthmus) on the medial edge of track, which are also features of <italic>Pteraichnus</italic>. This is the first occurrence of pterosaur tracks in Brazil, classified as <italic>Pteraichnus</italic> isp., increasing the ichnological diversity of the Botucatu Formation and also of the Brazilian geopaleontological heritage.

Key words
Botucatu Formation; Lower Cretaceous; paleodesert; Pteraichnus; Paraná Basin; tetrapod ichnology

INTRODUCTION

The Botucatu Formation (Paraná Basin) comprises one of the most emblematic aeolian geological units of the Lower Cretaceous of the Gondwana landmasses. This emblematic title is due to the fact that, to date, no body fossils – of vertebrates – have been recorded in this geological unit; on the other hand, there is a vast occurrence of trace fossils, including vertebrate and invertebrate tracks and trackways, especially of tetrapod fauna that shed light on the inhabitants of this ancient desert (Fernandes & Carvalho 2008, Buck et al. 2017a, Peixoto et al. 2020, Manes et al. 2021, Fernandes et al. 2024, Leonardi et al. 2024).

This giant desert (also known as paleoerg – related to an aeolian depositional system), which was located in the south-central portion of the Gondwana during the Jurassic–Cretaceous transition, is represented by a succession of cross-stratified sandstone facies that were deposited in a context of extreme aridity in a region of dunes and interdunes that covered a large area on both continents, South America, and Africa (Buck et al. 2017b, 2022, Peixoto et al. 2020, Fernandes et al. 2024). Despite being an arid region, a fluvial system was also identified in the lowermost portion of this paleodesert (Manes et al. 2021), probably providing conditions for the development of a complex faunal community at different trophic levels in the context of occasional humidity/rain events (Leonardi et al. 2007, Peixoto et al. 2020, Manes et al. 2021, Fernandes et al. 2024). Later, the entire Botucatu Formation was overlain by the volcanic layers of the Serra Geral Group (Fernandes & Carvalho 2007, Milani et al. 2007).

Although the first record of tetrapod tracks of the Botucatu Formation (also known as Botucatu Paleodesert – Francischini et al. 2020) are documented from 1911 (Leonardi & Sarjeant 1986, Leonardi et al. 2007, Fernandes & Carvalho 2008), research efforts began systematically at the end of the 20th century with the pioneering studies in this region (e.g. Leonardi 1980, 1981, Leonardi & Godoy 1980, Leonardi & Sarjeant 1986). These studies demonstrated the paleoichnological potential of the Botucatu Formation, and, since then, several studies have been carried out expanding knowledge of several aspects of the paleoichnology and geology of this formation (e.g. Buck et al. 2017a, b, 2022, Peixoto et al. 2020, 2024, Manes et al. 2021, Leonardi et al. 2024). As a result of this research effort, the largest known paleoichnological scientific collection of the Botucatu Formation is currently located in the Laboratório de Paleoecologia e Paleoicnologia (LPP) of the Universidade Federal de São Carlos (UFSCar) (see Fernandes et al. 2024, Leonardi et al. 2024). These fossil discoveries have provided and continue to provide great biological insight into the Early Cretaceous desert paleoecosystems of South America (e.g. Carvalho & Leonardi 2024).

Regarding the paleoichnological diversity of the Botucatu Paleodesert, in addition to the rich record of invertebrates, including trackways of arthropods and worm burrows (e.g. Leonardi 1980, Fernandes et al. 1990, but see Peixoto et al. 2020), several tetrapod tracks and trackways are known from this aeolian environment. Fossil records include squamate reptiles, probably Lacertilia (Buck et al. 2022); two morphotypes of ornithopod dinosaurs – with the smaller ones exhibiting gregarious behavior (Fernandes & Carvalho 2007, Fernandes et al. 2024); at least three morphotypes of theropod dinosaurs, including the ichnospecies Farlowichnus rapidus Leonardi et al. 2024, the ichnogenus Eubrontes (see Manes et al. 2021), and isolated footprints of a third ichnotaxon (Fernandes et al. 2024); and, mammaliaform ichnotaxa including Brasilichnium elusivum Leonardi 1981, B. saltatorium Buck et al. 2017a, B. anaiti D’Orazi Porchetti et al. 2018, and Aracoaraichnium leonardii Buck et al. 2017b; the latter two being probably synonyms (Peixoto et al. 2020, Buck & Fernandes 2024). Furthermore, silicified coniferous woods were found, at least on the edges, of the Botucatu Paleodesert (Pires et al. 2011). Moreover, there is also a micturalite recorded in the Botucatu Formation, which would represent a probable and unique liquid excretion of a dinosaur (Fernandes et al. 2004, Fernandes 2021). Based on this diverse ichnological fossil record, it is hypothesized that this desert paleoenvironment maintained favorable conditions to sustain a community at different trophic levels – ranging from detritivores/omnivores to top predators such as medium-size theropod dinosaurs (Leonardi et al. 2007, Peixoto et al. 2020, 2024, Manes et al. 2021, Fernandes et al. 2024).

This having been said, the aim of this study is to describe the first record of pterosaur tracks in the Lower Cretaceous (Berriasian–Barremian) Botucatu Formation. This new discovery, Pteraichnus isp., increases our knowledge about the diversity and potential paleoecological webs of the Botucatu Paleodesert; in addition, the new findings contribute to the increase of the Brazilian paleoichnological and geopaleontological heritage.

Geological and paleoenvironmental settings

The Botucatu Formation represents a geological unit of aeolian sandstones deposited in the great depression of the intracratonic Paraná Basin (Milani et al. 2007, Scherer & Goldberg 2007, Leonardi et al. 2024). The depositional age of the sandstones of the Botucatu Formation is considered as Early Cretaceous, Berriasian–Barremian (Renne et al. 1992, Brückmann et al. 2014, Fernandes et al. 2024).

The rocks of this thick package of dune deposits extend over 1,300,000 km2, cropping out mainly in Brazil, but also in Uruguay, Paraguay, Argentina, in South America, and Namibia and South Africa, on the African continent (Scherer & Goldberg 2007, Pires et al. 2011, Peixoto et al. 2020, Fernandes et al. 2024). In Brazil, the Botucatu Formation occurs mainly in the states of Rio Grande do Sul, Santa Catarina, Paraná, São Paulo, Minas Gerais, Mato Grosso do Sul, Mato Grosso, and Goiás, mainly on the edges and in the central region of the Paraná Basin, cropping out in the surface (Leonardi et al. 2007, 2024, Scherer & Goldberg 2007, Pires et al. 2011, Buck et al. 2017a, Peixoto et al. 2020, 2024, Manes et al. 2021, Fernandes et al. 2024).

The Botucatu Formation composes the São Bento Group in the Paraná Basin together with the Pirambóia and Serra Geral formations. Part of the sandstones of the Botucatu Formation are, to a large extent, interspersed with basalts belonging to the Serra Geral Group (Leonardi et al. 2007, Fernandes & Carvalho 2008). The sedimentary structures commonly found in this formation are tangential cross-strata, which, towards the top, pass to plane-parallel and channeled sandstone cross-strata (Fernandes et al. 2024). The main geological composition of the Botucatu Formation is aeolian facies of fine to well-sorted fine- to medium-grained quartzose sandstones that were deposited on dunes influenced by N and SW monsoon winds (Scherer & Goldberg 2007, Buck et al. 2017a, Manes et al. 2021, Peixoto et al. 2024), agreeing with the global wind circulation pattern modeled for the Late Jurassic in the Southern Hemisphere (Scherer & Goldberg 2007).

During the Early Cretaceous, the Botucatu Formation represented some “sub environments” in a context of large desert or semi-deserts of increasing aridity, whose existence in the south-central portion of Gondwana lasted until the basaltic volcanism events derived from fissure eruptions associated with the drift between Africa and South America (Pires et al. 2011, Manes et al. 2021, Fernandes et al. 2024, Carvalho 2024, Peixoto et al. 2024). The paleoenvironment resembled current sandy deserts with arid conditions represented by an extensive field of medium and large size dunes, probably with interdunal valleys that presented some degree of precipitation and residual channel deposits at their base (Pires et al. 2011, Buck et al. 2017a, Manes et al. 2021, Fernandes et al. 2024).

MATERIAL AND METHODS

Locality

The new specimens were recovered from the reddish to yellowish sandstones of the Ouro ichnosite, São Bento Quarry (21°49’03.4”S/48°04’22.9”W), Municipality of Araraquara, State of São Paulo, Brazil (figure 1). As previously noted, the São Bento quarry has the section of a large dune with at least 20 m high and 100 m in total length. In addition, it presents features of foreset, one of the three possible sedimentation strata in dunes; the layers are formed by sediments deposited on the sliding face at an angle of repose (Mikes & Bruining 2006), with the dip angle in the Ouro ichnosite being c.30° S-SW (Leonardi et al. 2007, 2024, Fernandes & Carvalho 2008, Buck et al. 2017a, b, Peixoto et al. 2020, Fernandes et al. 2024). The Ouro ichnosite (sensu Leonardi & Carvalho 2002) is well-known and a prominent outcrop concerning the great abundance and diversity of trace fossils from South America (Leonardi & Carvalho 2002, Fernandes & Carvalho 2008, Leonardi et al. 2024, Peixoto et al. 2024); and probably the more representative of this formation. From this outcrop, the fossil materials exemplify the final moments of deposition in this ancient desert and are therefore materials from the top of the Botucatu Formation (Fernandes & Carvalho 2008).

Studied specimens

Both specimens LPP-IC-0232 and LPP-IC-0233 are deposited in the scientific collection of the Laboratório de Paleoecologia e Paleoicnologia (LPP) of the Universidade Federal de São Carlos (UFSCar); all the materials had been acquired by the institution in previous fieldwork during the years 1997 and 2006 (see Buck et al. 2017a, Fernandes et al. 2024). Although there is a lack of precision regarding the stratigraphic levels of the materials studied, both slabs come from the same location, from the same ichnofossiliferous level or from similar levels, in a region represented by an outcrop in the upper section sandstones of the Botucatu Formation. Specimen LPP-IC-0232 was referred to as MPA-625 in Fernandes (2005) and here renumbered within the LPP scientific collection. Each specimen represents an individual block, or slabs, typical of those used in the region for commercial purposes, mainly for paving sidewalks (Buck et al. 2017a, Francischini et al. 2020, Leonardi et al. 2024). LPP-IC-0232 is an isolated rectangular flagstone (39 cm long, 32 cm wide, and 11 cm thick) and LPP-IC-0233 is an isolated irregular flagstone (62 cm long, 37 cm wide, and 5 cm thick).

Ichnological description and track comparison

We based our descriptions following the convention proposed by Leonardi (1987) and Lallensack et al. (2025). We discuss the main features of the tracks and potential diagnoses according to the criteria discussed by Billon-Bruyat & Mazin (2003) as well as descriptions of Stokes (1957) and Lockley et al. (1995). Our comparisons were made through direct study of dozens of isolated tracks and footprints from the Botucatu Formation, including materials already described in the literature (e.g. Buck et al., 2017a,b, Fernandes et al. 2024, Leonardi et al. 2024) as well as other tracks/trackways from LPP/UFSCar under study.

Our directional reference (anterior, posterior, etc.) is based on the morphology of the pterosaur footprint widely explored in the literature, and well established from well-preserved trackways, following: Stokes (1957), Billon-Bruyat & Mazin (2003), Mazin et al. (2003), Mickelson et al. (2004), Lee et al. (2008, 2010), Xing et al. (2013), Hernández-Medrano et al. (2017), Elgh et al. (2019), Li et al. (2021, 2024), Ha et al. (2022), Jung et al. (2022), Heredia et al. (2024), and Jung & Huh (2024).

Measurements and multivariate analysis

Linear measurements and angulations used in comparisons with other pterosaur tracks follows Mazin et al. (2003), Lee et al. (2010), Hernández-Medrano et al. (2017), and Heredia et al. (2024) as follows: Lp, length of pes imprint; Wp, width of pes imprint; Lm, length of manus imprint; Wm, width of manus imprint; LI, LII and LIII, manus digit imprints length I, II and III; D I–II, II–III and I–IIII interdigital divarication angles between digit imprints I and II, II and III, and, I and III; Lmt, length of metatarsal imprint; Ld, length of digital portion of pes imprint (as indicated in figure 2). Track measurements were performed using a digital caliper (measurement range: 0–150 mm; resolution: 0.01 mm) and measured directly on the tracks. All angles were obtained using the software ImageJ v.1.53e (Schneider et al. 2012).

Several morphometric variables were compared using PAST v4.01 software (Hammer et al. 2001) extracting pterosaur footprint metrics originally compiled by Li et al. (2021), and data from Rodríguez-De La Rosa (2003), Whyte & Romano (2014), Ha et al. (2022), and Heredia et al. (2024) were also included in the analysis/comparisons. The following metrics: Lp, Wp, Lm, Wm, D I-II, D II-III, Lmt, and Ld were logarithmically transformed and subjected to a Principal Component Analysis (PCA), based on a variance-covariance matrix, reducing the dimensionality of the data and thus generating a morphospace with the distribution of the pterosaur track based on the analyzed metrics (Table I).

Table I
Set of measurements, angles, and ratios extracted from pterosaur footprints and used in the comparisons performed in this work (see abbreviations in Material and Methods).

Ichnotaxa	Lp x Wp	Lm x Wm	Divarication		Ld x Lmt	Lp/Wp	Lm/Wm	Ld/Lmt
			I-II	II-III
Ramphichnus crayssacensis	2.91 x 0.52	3.13 x 0.55	14.8°	22.5°	24.7 x 4.4	5.6	5.69	5.61
Ramphichnus pereiraensis	2.40 x 1.73	2.40 x 0.96	6.4°	17.2°	1.71 x 0.69	1.39	2.5	2.48
Ramphichnus lafaurii	1.68 x 1.45	2.17 x 0.74	7°	12°	?	1.16	2.93	?
Purbeckopus pentadactylus	18.70 x 9.8	14 x 8.5	22.9°	79º	11.82 x 6.88	1.91	1.64	1.72
Agadirichnus elegans	9.16 x 3.13	6.21 x 3.09	64.6°	34.4°	4.67 x 4.49	2.93	2	1.04
Haenamichnus uhangriensis	35 x 10.5	33 x 11	?	?	?	3.33	3	?
Pteraichnus saltwashensis	8.76 x 4.33	8.20 x 3.15	43.4°	48.1°	3.71 x 5.05	2.02	2.6	0.73
Pteraichnus stokesi	9 x 4.10	7 x 3.4	13.7°	31°	4.48 x 4.52	2.2	2.05	0.99
Pteraichnus parvus	1.53 x 1.14	2.46 x 1.2	64°	58°	0.44 x 1.09	1.34	2.05	0.4
Pteraichnus longipodus	3.4 x 1.74	2.45 x 1.67	47°	49°	?	1.95	1.46	0.22
Pteraichnus koreanensis	2.57 x 1.28	2.56 x 1.23	68.5°	47.6°	0.1 x 1.76	2.01	2.08	0.46
Pteraichnus palacieisaenzi	15.34 x 11.9	13.02 x 4.85	75.9°	56.2°	8.67 x 6.67	1.29	2.68	1.3
Pteraichnus dongyangensis	9 x 3	6.5 x 4	52°	29°	?	3	1.62	?
Pteraichnus nipponensis	1.94 x 1.05	2.01 x 0.88	83.18°	81.70°	0.47 x 1.23	1.85	2.28	0.38
Pteraichnus yanguoxiaensis	12.3 x 3.6	12.2 x 4.8	60.7°	53.9°	?	3.42	2.54	?
Pteraichnus isp. (Herein)	18.2 x 6.9	18.7 x 11.4	30°	86°	3.6 x 14.6	2.63	1.64	0.24
Pteraichnus isp. (China)	14 x 6	12.30 x 5.2	58°	70°	6.07 x 7.93	2.33	1.98	0.77
Pteraichnus isp. (Mexico)	13.2 x 4.6	6.9 x 3.4	39°	64°	?	2.86	2.02	?
Pteraichnus isp. (UK)	5.2 x 3.15	5.9 x 2	70°	76°	?	1.65	2.95	?
Pteraichnus isp. (Argentina)	11 x 4.4	9.9 x 4.8	48°	75°	2.9 x 7.2	2.5	2.06	0.4

Hip height estimation

As is widely known, there is a correlation between hip height and total foot track length in several dinosaur clades (Thulborn & Wade 1984, Thulborn 1984, 1990, Fernandes 2005, Weems 2006), which is an important source of biological information in vertebrate paleoichnology studies. However, this type of study on pterosaur footprints and skeletal specimens has only recently been explored; Li et al. (2024) investigated several metrics in 54 pterosaur (35 pterodactyloids) and based on this, generated equations that associate pes track length (x) with hip height (y) in this clade. Thus, equation (1) for pterodactyloids provided by Li et al. (2024) was adopted here in the inference about hip size in the ichnotaxon under study – allowing more detailed comparisons.

$$y=3.200x+14.798$$ (1)

Digital models

3D digital models of the tracks were generated using a surface scanner (RevoPop, accuracy up to 0.05 mm). Based on the generated 3D files, CloudCompare v2.7.0 (2025) software was used to obtain false color height map images of the tracks. The 3D digital models of LPP-IC-0232 and LPP-IC-0233 are available via MorphoSource (https://www.morphosource.org/projects/000681574), thus providing the access (and digital handling) to the textured meshes for comparisons and interpretations by ichnologists, as suggested by Falkingham (2014).

RESULTS

Systematic paleoichnology

Ichnofamily Pteraichnidae Lockley et al. 1995

Ichnogenus Pteraichnus Stokes 1957

Type-ichnospecies Pteraichnus saltwashensis Stokes 1957

Pteraichnus isp.

Referred material. Isolated impressions of manus LPP-IC-0232 and pes LPP-IC-0233 preserved in the “Botucatu sandstone” in concave epirelief (original tracks).

Horizon and locality. Ouro ichnosite, São Bento Quarry, Botucatu Formation (top of this aeolian depositional unit), São Bento Group (Paraná Basin), Municipality of Araraquara, São Paulo State, Brazil (figure 1).

General features. Large quadrupedal trackways (see below); asymmetrical, digitigrade manus (manus length:width ratio = c.1.64); digits with parallel lateral edges; claw of digit I “hooked” and laterally oriented, claw of digit II “hooked” and anteriorly oriented; claw of digit III straighter medially than laterally, elongated and posteriorly oriented; most distal phalanx/ungual of digit III slightly adducted (medial direction); angle between the digits of the manus: I-II (30.1°), I-III (116.6°), and II-III (86.6°); asymmetrical, rectangular shape and plantigrade pes impression (pes length:width ratio = c.2.63); metatarsal length about four times greater than digital length; tridactyl impression with digits equivalent in total length but varying in total width; medial border of pes with “S” impression; medial digit with triangular claw impression and pads.

Description of the tracks

Manus track. LPP-IC-0232 is an isolated and well-preserved digitigrade, tridactyl autopodial impression of the left manus (figure 2a-c). There is no sediment filling the handprint cavities, and it is considered an “original track”, different from the undertrack pattern of specimens from the Botucatu Formation (Fernandes et al. 2024). The track is asymmetrical, being longer than it is wide (length 18.7 cm; width 11.4 cm; figure 2g). No pad impression is noted in this specimen. The imprint of digit I is oriented anterolaterally, impression of digit II is oriented laterally, whereas impression of digit III is facing backwards (figure 2a-c). Digit length increases I<II<III, with digit III being relatively elongated and curved posteriorly (digital length: I = 7.1 cm; II = 11 cm; III = 16.9 cm; figure 2g). Proximodistally, all digits have parallel lateral borders; the widths of digits I, II, and III are 2.3 cm, 2.3 cm, and 2.4 cm, respectively. The claw impression on the distal end of each digit is preserved; the claw trace of digit III is slightly straight on the medial side, but with a more pronounced curvature on the lateral side, being long and oriented posteromedially (estimated length c.3.7 cm), whereas the claws of digits I and II are similar in size (estimated length c.2.7 cm and c.2.8 cm respectively) (figure 2a-b). Moreover, the claw traces of digits I and II have a pronounced curvature, giving it a “hook-shape” (figure 2a,g, figure 4a); the claw of the digit I is oriented laterally and the claw of digit II oriented anteriorly (figure 2a). The hypexes in LPP-IC-0232 are “U-shaped”. The divarication angle of each digit indicates an acute angle between digits I-II and digits II-III, whereas an obtuse angle is noted between digits I-III (I-II = c.30.1°; I-III = c.116.6°; II-III = c.86.6°; figure 2g). It is interesting to note that although the digit III is facing backwards, probably the penultimate phalanx and the last (the ungual) were turned slightly medially during the production of the track (figure 2a-c). The outline of the manus imprint can be easily distinguished, especially on the lateral part due to the angle of inclination of the dune surface (c.30° – Fernandes & Carvalho 2008); providing a deeper impression of the anterolateral portion of the track (figure 2c). The medial contour of the autopodial impression is slightly lighter, probably related to the slope of the dune surface; however, it has a “half-moon” shape with no clear evidence of the impression of digit IV.

Pes track. LPP-IC-0233 is an isolated and well-preserved plantigrade, tridactyl impression of the left pes (figure 2d-f). Similar to LPP-IC-0232, the pes impression LPP-IC-0233 is also distinguishable from undertracks of the Botucatu Formation (Fernandes et al. 2024), being probably an “original track” with a small sandstone filling part of the posterior cavity of the track. The pad impression can be seen on the median digit (figure 2d,f). The track is nearly asymmetrical (with a medial curvature), being much longer than it is wide (approximately 3 times longer; length c.18.2 cm; width c.6.9 cm; figure 2d-g). The elongated track is rectangular in shape, with the posterior edge of the heel pad clearly rounded in a “U-shape” (figure 2d-f). The medial edge of the pes imprint has a “sinusoidal” or “S” shape, causing a pronounced rounded indentation on the medial to distal portion of the metatarsals on the medial side (or a midfoot arch known as pedal isthmus; Lallensack et al. 2025) (figure 2e,f). The lateral side of the track appears to be straight, especially based on the posterior portion (see pes track production below). The metatarsal region is approximately four times longer than the digital region (metatarsal length c.14.6 cm; digital region length c.3.6 cm) (figure 2d-f). Three digits are observed, being short and positioned anteriorly (distally); equivalent in total length and varying in width (digital length: medial digit = c.1.0 cm; intermediate digit = c.1.7 cm; lateral digit = c.1.8 cm; figure 2g). The most medial digit (probably related to the left digit I, considering later-diverging pterodactyloids – Beccari et al. 2021) is the narrowest, the medial digital impression (probably related to digit II) is broad with a markedly rounded anterior edge, and the most lateral digital impression (probably related to the digit III or both digits III and IV) is deeper and has a width equivalent to that of the medial digit impression (figure 2d-f). The boundaries between the digits are very subtle. It is interesting to note that in the impression of the median digit (probably digit II), distal to its anterior rounded edges, there is a very faint impression of a “triangle-shaped” claw (estimated length c.1.5 cm); the most medial digit (probably digit I) also has a trace that may represent a small “needle-like” claw – no claw track clues are observed on the lateral digit(s) of LPP-IC-0233 (figure 2e,f).

Comparisons with dinosaur tracks

The manus imprint (LPP-IC-0232) is digitigrade and tridactyl, similar to theropod and ornithopod dinosaur tracks. However, several other features distinguish LPP-IC-0232 from tridactyl dinosaurs, as follows. Fernandes et al. (2024) although they interpreted digit III differently, noted that LPP-IC-0232 is a track wider than long, presenting “U-shaped” hypexes and larger interdigital angles. These features previously observed by Fernandes et al. (2024) differentiate LPP-IC-0232 from tridactyl dinosaur track morphotypes in general, which are longer [or slightly longer] than wide, with a “V-shaped outline” in most theropods or with a “rounded” outline in ornithopods with a “U-shaped” posterior margin (e.g. Lockley 1998, Fernandes & Carvalho 2007, Xing et al. 2021, Fernandes et al. 2024, Leonardi et al. 2024, Navarro et al. 2025).

Another striking feature in LPP-IC-0232 is the impression of a long digit (III) pointing backwards (figure 2); typically in theropods, the longest digit is also the digit III, but in a completely different configuration, where digit III is centrally positioned in a mesaxonic-shaped footprint with asymmetric interdigital angles with a “V-shaped” hypex (e.g. Manes et al. 2021, Fernandes et al. 2024, Leonardi et al. 2024, Navarro et al. 2025). If a theropod had been the trackmaker, the most elongated digit would be the median one, not the most lateral one; this posteriorly elongated digit gives the track a rhombic shape and overall asymmetry (figure 2), differing from the pattern observed in theropod and ornithopod dinosaur tracks. Furthermore, the laterally marked claw trace on specimen LPP-IC-0232 differs from that of dinosaurs. Fernandes et al. (2024) also noted that in LPP-IC-0232 the digits are relatively thin and straight on their lateral and medial edges proximodistally. Although these are subtle features, they help to differentiate the studied material from tridactyl dinosaur tracks, especially those from Botucatu Formation (e.g. Fernandes & Carvalho 2007, Fernandes et al. 2024, Leonardi et al. 2024).

Additionally, the pes imprint (LPP-IC-0233) is clearly that of a plantigrade tetrapod, with the metatarsal region about four times longer than the digital region, and three anteriorly positioned pedal digits imprint (figure 2). This feature is not observed in any dinosaur, or in other tetrapods from the Botucatu Formation (e.g. Aracoaraichnium; Buck et al. 2017b). LPP-IC-0233 also has the midfoot arch [pedal isthmus] on the medial edge of the track, although this feature is common in humans (Lallensack et al. 2025), it is also present in pterosaurs (Calvo & Lockley 2001, Lee et al. 2008, Chen et al. 2013, Li et al. 2024).

Thus, the features listed above: “U-shaped” hypexes, higher interdigital angles, rhombic and asymmetric morphology, the presence of lateralized claws and the impression of a large digit posterior to the manus impression in LPP-IC-0232; and the metatarsal region being much longer than the digital region, the presence of three digits and the midfoot arch on the medial edge of the pes impression in LPP-IC-0233 are striking features that differentiate the materials described here from tridactyl dinosaur and other tetrapod tracks. Furthermore, as discussed in more detail below, this set of features is diagnostic and allows us to identify the trackmaker as a pterosaur based on Stokes (1957), Lockley et al. (1995), Calvo & Lockley (2001), Billon-Bruyat & Mazin (2003), Mickelson et al. (2004), Lee et al. (2008, 2010), Xing et al. (2013), Hernández-Medrano et al. (2017), Elgh et al. (2019), Li et al. (2021, 2024), Ha et al. (2022), Jung et al. (2022), Heredia et al. (2024), and Jung & Huh (2024).

Probable differential diagnosis of LPP-IC-0232 and LPP-IC-0233

There are at least three ichnogenera related to pterosaurs trackmakers: Pteraichnus, occurring from the Late Jurassic to Middle Cretaceous, and larger forms such as Purbeckopus and Haenamichnus, and probably Agadirichnus, all occurring in the Cretaceous (Wright et al. 1997, Hwang et al. 2002, Lockley et al. 2008, Sánchez-Hernández et al. 2009, Kim et al. 2012, Masrour et al. 2018). Among these, Pteraichnus represents an abundant and biodiverse ichnogenus (Jung et al. 2024).

The first record of pterosaur fossil tracks was recovered from the Jurassic Morrison Formation (United States) and was originally described and named as the ichnospecies Pteraichnus saltwashensis Stokes 1957. Since then, despite some controversy (e.g. Padian & Olsen 1984) and a long debate lasting years among experts’ ichnologists, there has been an increase in the number of ichnospecies and global occurrences of Pteraichnus (Lockley et al. 2008, Sánchez-Hernández et al. 2009), as well as changes to the original diagnosis.

Following Stokes (1957), Lockley et al. (1995), and Billon-Bruyat & Mazin (2003), Pteraichnus can be diagnosed, among others, by the following characteristics: (1) quadrupedal trackways – digitigrade manus and plantigrade pes imprint; (2) elongated, sub-triangular and tetradactyl pes imprint; (3) pedal digits II and III slightly longer than I and IV; (4) pedal digits I-IV clawed; (5) asymmetrical, elongated and tridactyl manus imprint; (6) manual digits increase in length I<II<III; (7) digit I oriented anteriorly/anterolaterally usually with claw trace; (8) digit II oriented anterolaterally/posterolaterally rarely with claw trace; (9) digit III oriented posteriorly exceptionally with claw trace; (10) rounded margin of the manus imprint in the medial region; and (11) digit IV rarely marks the posteromedial region of the manus imprint.

Based on these features, LPP-IC-0232 and LPP-IC-0233 are assigned to Pteraichnus. Based on the redefinition given by Billon-Bruyat & Mazin (2003), the pes imprint LPP-IC-0233 studied here differ from subtriangular and tetradactyl imprints listed as Pteraichnus, being sub-rectangular and tridactyl (figure 2d-f). However, Heredia et al. (2024) suggested that tridactyl pes could be a new diagnostic feature, being relatively common in the ichnological fossil record of Pteraichnus (e.g. Kim et al. 2006, Xing et al. 2013, Heredia et al. 2024). Furthermore, sub-rectangular rather than subtriangular or “Y-shaped” imprints are also features observed in several Pteraichnus tracks worldwide (e.g. Peng et al. 2004, Hernández-Medrano et al. 2017, Heredia et al. 2024) as well as in LPP-IC-0233 described here (as presented below).

We summarized here and discuss below the following characteristics considered for the attribution of the new fossil tracks to the ichnogenus Pteraichnus: ratio of manus length:width (c.1.64); claw of digit I “hooked-shaped” and laterally oriented, claw of digit II “hooked-shaped” and anteriorly oriented; claw of digit III straighter medially than laterally, elongated and posteriorly directed; penultimate and distal phalanx (ungual) of digit III slightly adducted; angle between the digits of the manus, digits I-II (30.1°), digits I-III (116.6°), and digits II-III (86.6°); ratio of pes length:width (c.2.63); length of the metatarsal four times the digital length; medial border of the metatarsals imprint “S-shaped”; medial digit of the pes with triangular claw impression; and finally the “large” size of the tracks (c.18 cm in total length – discussed below).

Manus track comparison

The manus imprint of Pteraichnus isp. LPP-IC-0232 differs from Pt. saltwashensis, Pt. stokesi Lockley et al. 1995, Pt. koreanensis Lee et al. 2008, Pt. nipponensis Lee et al. 2010, Pt. dongyangensis Chen et al. 2013, Pt. wuerhoensis Li et al. 2021, Pt. gracilis Ha et al. 2022, and Pteraichnus isp. (e.g. He et al. 2013, Heredia et al. 2024), by the presence of three well-preserved claw traces, with the claw of digit III being elongated with a gentle curvature (figure 2). Most of the ichnospecies mentioned above have evidence of at least two claws (usually on digits I and II), but in some cases only one claw trace is present (e.g. Pt. saltwashensis, Pteraichnus isp. Hernández-Medrano et al. 2017), or none (i.e. Pt. wuerhoensis). Regarding the morphology of the ungual of digit III in LPP-IC-0232, the only form that resembles its elongated and nearly straight claw is Pt. nipponensis from the Lower Cretaceous of Japan (Lee et al. 2010); however, there are considerable differences in the size of both ichnotaxa. In Pteraichnus isp. LPP-IC-0232, the claw trace of digits I and II are “hooked”, similar to several other Pteraichnus, but the claw of digit I is positioned laterally and that of digit II is positioned anteriorly, giving a “rounded pincer” appearance when both unguals are considered. Generally, the claw trace of digit I is anteriorly oriented as in Pt. gracilis, Pt. nipponensis, and Pteraichnus isp. from Poland and Spain (Lee et al. 2010, Hernández-Medrano et al. 2017, Elgh et al. 2019, Ha et al. 2022), or more anterolateral as in Pt. saltwashensis and Pt. dongyangensis (Stokes 1957, Chen et al. 2013) – differing from LPP-IC-0232.

In Pteraichnus isp. LPP-IC-0232 the digits have regular width throughout their entire length, i.e., with parallel lateral borders (figure 2); this differs from some more irregular digit impressions noted in Pteraichnus isp. (He et al. 2013, Heredia et al. 2024) and Pt. wuerhoensis (Li et al. 2021), and the “subtriangular and sometimes blunt” digit as seems in a Pteraichnus isp. from Mexico (Rodríguez-De La Rosa 2003); besides that, LPP-IC-0232 resembles, in a proportionally distinct way, the narrow digit traces of Pt. nipponensis and Pt. dongyangensis (Lee et al. 2010, Chen et al. 2013).

The presence of a very elongated digit III printing backwards is a common feature of Pteraichnus (e.g. Stokes 1957, Lockley et al. 1995, Calvo & Lockley 2001, Billon-Bruyat & Mazin 2003, Li et al. 2021, Díaz-Martínez et al. 2022, Heredia et al. 2024). Generally, these digits are straight and directed posteriorly, as in Pt. dongyangensis, Pt. gracilis, Pt. koreanensis, and some forms of Pteraichnus isp. from Argentina, Korea, and Poland (Lee et al. 2008, Chen et al. 2013, Ha et al. 2018, Elgh et al. 2019, Ha et al. 2022, Jung et al. 2022, Heredia et al. 2024); however, digit III can also be oriented posteriorly with a medially directed (mediodistal) curvature as in Pteraichnus yanguoxiaensis Peng et al. 2004, Pt. saltwashensis, Pt. stokesi, Pt. wuerhoensis and some forms of Pteraichnus isp. from China, Mexico, the United States, and the United Kingdom (Stokes 1957, Lockley et al. 1995, Mickelson et al. 2004, Rodríguez-de La Rosa 2003, He et al. 2013, Whyte & Romano 2014, Li et al. 2021). In Pteraichnus isp. LPP-IC-0232, the third manual digit trace is also posteriorly oriented and medially directed, however this condition seems to be exacerbated, since the most distal phalanx and ungual are slightly adducted (figure 2).

Finally, the medial edge of the manus imprint in LPP-IC-0232, Pt. stokesi, and Pt. dongyangensis (Lockley et al. 1995, Chen et al. 2013) has a rounded morphology, even with distinctly curved edges (e.g. rhombic-shape – Díaz-Martínez et al. 2022); however, it differs from Pt. gracilis, Pt. koreanensis, and some Chinese Pteraichnus isp., which have a straighter medial border (Lee et al. 2008, Xing et al. 2012, Ha et al. 2022), whereas this feature in Pt. wuerhoensis (Li et al. 2021) appears to be more variable.

Pes track comparison

As previously mentioned, the pes imprint of Pteraichnus isp. LPP-IC-0233 differs from ichnotaxa such as Pteraichnus palacieisaenzi Pascual Arribas & Sanz Pérez 2000, Pteraichnus junggarensis Li et al. 2024, Pt. saltwashensis, Pt. stokesi, Pt. gracilis, Pt. koreanensis, Pt. nipponensis, Pt. wuerhoensis, and some forms of Pteraichnus isp. from China, Mexico, Poland, Korea, and the United States (Stokes 1957, Lockley et al. 1995, Rodríguez-De La Rosa 2003, Mickelson et al. 2004, Lee et al. 2008, 2010, He et al. 2013, Elgh et al. 2019, Li et al. 2021, Ha et al. 2022, Jung et al. 2022) by the presence of only three short digits instead of four digits (tetradactyl pes impression). However, as noted by Heredia et al. (2024), there are some records that preserve three pedal digit imprints, such as the Argentinean and South Korean Pteraichnus isp. (Kim et al. 2006, Heredia et al. 2024); these differences may have ichnotaxonomic significance (Heredia et al. 2024). However, taphonomic explanations cannot be ruled out (e.g. Marchetti et al. 2019).

In some fossil forms, the interphalangeal separation is quite extensive and clear, as in Pt. dongyangensis, Pt. gracilis, Pt. koreanensis, Pt. wuerhoensis, and some forms of Pteraichnus isp. from Mexico, Argentina, and South Korea (Rodríguez-de La Rosa 2003, Lee et al. 2008, He et al. 2013, Li et al. 2021); differing from Pteraichnus isp. (LPP-IC-0233) and Pteraichnus isp. from South Korea (Kim et al. 2006) with a very short digital region. In some Pteraichnus isp. (e.g. Rodríguez-De La Rosa 2003) the pedal digits are slightly longer than others, in Pteraichnus isp. LPP-IC-0233 the digits are almost equivalent in total length. Ichnotaxa with the longest digits in proportion to the metatarsals (Ld/Lmt) are Pt. palacieisaenzi (1.3), Pt. wuerhoensis (1), Pt. stokesi (0.99), Pt. juggarensis (0.78), and Pt. saltwashensis (0.73); metatarsals proportionally longer than the digits are noted in Pt. koreanensis (0.46), Pt. nipponensis (0.38), Pt. longipodus (0.22) (Li et al. 2024), as well as Pteraichnus isp. LPP-IC-0233 (0.24).

The morphology of the pes imprint in Pteraichnus is variable, being an important informative feature in the ichnotaxonomy of the clade (Billon-Bruyat & Mazin 2003, Díaz-Martínez et al. 2022). LPP-IC-0233 has a sub-rectangular shape of the pes imprint, similar with Pt. dongyangensis, Pt. yanguoxiaensis, and some forms of Pteraichnus isp. from Mexico, China, and South Korea (Rodríguez-de La Rosa 2003, Peng et al. 2004, Kim et al. 2006, Chen et al. 2013, Xing et al. 2013). In other cases, the pes imprint has a sub-triangular to triangular shape, such as in Pt. saltwashensis, Pt. stokesi, Pt. gracilis, Pt. wuerhoensis, and some forms of Pteraichnus isp. from Argentina and China (Stokes 1957, Lockley et al. 1995, He et al. 2013, Li et al. 2021, Ha et al. 2022, Heredia et al. 2024). Furthermore, differing from Pteraichnus isp. LPP-IC-0233, some pes imprints have an “Y” shaped, as noted in Pt. nipponensis, Pt. koreanensis and Pteraichnus isp. from Spain (Lee et al. 2008, 2010, Hernández-Medrano et al. 2017). More evident “V” shaped heel edges can be seen in Pt. palacieisaenzi, Pt. saltwashensis, Pt. stokesi, Pt. koreanensis, and some forms of Pteraichnus isp. from Argentina (Stokes 1957, Lockley et al. 1995, Lee et al. 2008, Pascual-Arribas et al. 2014, Heredia et al. 2024); otherwise, a “U” shaped heel edges are a feature share among Pteraichnus isp. LPP-IC-0233, Pt. wuerhoensis, Pt. dongyangensis, and some forms of Pteraichnus isp. from Mexico, China, and South Korea (Rodríguez-de La Rosa 2003, Kim et al. 2006, Chen et al. 2013, Xing et al. 2013, Li et al. 2021).

Finally, the metatarsal length in LPP-IC-0233 is about four times greater than the digital region length (metatarsal length c.14.6 cm; digital region length c.3.6 cm) (figure 2). The medial border of the pes imprint (metatarsal portion) has a smooth “S” shaped configuration, this curve is also seen in Pt. koreanensis and even smoother in Pt. dongyangensis, (Lee et al. 2008, Chen et al. 2013). Other ichnotaxa such as Pteraichnus isp. from Korea (Ha et al. 2018) have a slightly “U” shaped medial curve of the metatarsal or is it straighter as in Pteraichnus isp. from Mexico and China (Rodríguez-de La Rosa 2003, He et al. 2013). Thus, both fossil tracks described here present diagnostic features of Pteraichnus and some distinct and unique morphological features that are probable related to a new ichnotaxon.

REMARKS

General comments on LPP-IC-0232 and LPP-IC-0233 tracks

As previously noted, the materials described here come from previous collections carried out between 1997 and 2006 (Buck et al. 2017a, Fernandes et al. 2024) and refer to distinct slabs, LPP-IC-0232 (manus imprint) and LPP-IC-0233 (pes imprint), presenting two isolated fossil footprints. Two other pieces of evidence for the production of the tracks at different episodes are provided by the degree of humidity in the substrate, which was apparently higher when track LPP-IC-0232 was produced compared to LPP-IC-0233 (evidenced by the pattern on the sand surface and collapse of the substrate). Furthermore, the locomotor activity that can be associated with each track, based on previous knowledge about the degree of inclination of the dunes of the Botucatu Paleodesert, suggesting the downward movement on the dune in LPP-IC-0232 and upward movement in LPP-IC-0233, highlights two moments and two distinct activities (figure 2c, f).

However, although they are isolated fossil tracks, we associate both with the same producer as follows: (1) The specimens were recovered from the same locality (Ouro ichnosite – Leonardi & Carvalho 2002; figure 1) and they probably come from the same ichnocenosis; (2) As discussed below, both LPP-IC-0232 and LPP-IC-0233 exhibit diagnostic features that allow association of these tracks to the ichnogenus Pteraichnus (Stokes 1957, Lockley et al. 1995, Billon-Bruyat & Mazin 2003), while they also possess unique features; and, (3) Finally, considering the fossil track of pterodactyloid pterosaurs, it is generally observed that the same individuals present the total length of the manus and pes imprint equivalent (see below), or quite similar as observed in Purbeckopus pentadactylus Delair 1963 and in the various occurrences of Pteraichnus (Stokes 1957, Lockley et al. 1995, Wright et al. 1997, Rodríguez-de La Rosa 2003, Fiorillo et al. 2009, Lee et al. 2008, Heredia et al. 2024). The materials described here have the total length of the manus and pes imprint proportional to each other (see discussion on size below), therefore we speculate that both fossil tracks were produced by the same individual. However, if the fossil tracks were produced by different individuals (due to gregariousness, for example), which is not ruled out, then the distinct individuals would necessarily have to present equivalent body size to explain the correlation between the total length of the tracks (figure 4a).

Figure 1
Geological map of the Paraná Basin, highlighting the Ouro Ichnosite, Botucatu Formation, Municipality of Araraquara, São Paulo State, Brazil. Modified from Leonardi et al. (2024).

Figure 2
Photographs and outline drawings of the Pteraichnus isp. from the Lower Cretaceous Botucatu Formation. Manus imprint LPP-IC-0232. (a) fossil track photograph, (b) 3D digital model, (c) depth map. Pes imprint LPP-IC-0233. (d) fossil track photograph, (e) 3D digital model, (f) depth map. (g) outline drawings and extracted measurements/angles (see abbreviations in Material and Methods).

Track production

Considering the manus track, LPP-IC-0232, the greatest effort in the impression of the fossil track is made by digit II, more deeply excavated in the sandy substrate, whereas digits I and III are less deeply excavated, respectively (figure 2c). There is a pattern of small, repeated or successive crenulations (sand movements) observed in LPP-IC-0232 that suggests a small rotational effort of the manus during the production of the track (figure 2a-c), which may eventually have been produced by the humidity level of the sand. This may have been caused by the autopodium resting on the substrate in two movements, the first support rotating clockwise until the final support and handprint; thus, collapsing the edges of digit II and the medial region of the autopodium. This track appears to have been produced on a substrate with a moderate degree of humidity (as previously proposed by Leonardi 1980, see also Peixoto et al. 2024), which allowed good preservation of the main boundaries of the autopodial impression. Additionally, based on the sand collapses observed at the lateral edge of the impression in LPP-IC-0232 and the already known inclination angle of c.30° of the dunes of the Botucatu Paleodesert, it is possible to infer that the producer performed the downward movement on the dune, at an oblique angle to the main axis (and ridge) of the dune.

Regarding the pes track production, in the specimen LPP-IC-0233, the greatest stress in the track is noted in the mediodistal portion of the metatarsus, deeper into the sandy substrate – this is expected considering an impression of a plantigrade quadruped – the heel portion and the digital portion are marked more superficially (figure 2d-f). In the anterior part of the track, there are crenulation lines in the sand, these lines differ from those observed in the manus imprint (which were derived from rotation) (figure 2d-f). Furthermore, the sand crenulations show the collapse of the substrate with the step, subsequently, there was a collapse of sand from the mediodistal part of the lateral edge of the metatarsals into the cavity of the track, probably due to gravity – even so, most of the lateral edges remained preserved, allowing an inference of a straighter lateral edge for this track. Probably there was also a sand collapse in correspondence of the tip of the potentially assembled digits (III-IV). Finally, distinct of the manus impression, based on the strong displacement rim around the heel pad (without crenulations; figure 2f), associated with the dune inclination of c.30°, it is possible to infer the upward movement of the producer obliquely to the main axis, and ridge of the dune.

Fernandes et al. (2024) demonstrated that some theropod tracks from the Botucatu Formation can be preserved with some inward curvature; expressing a high degree of curvature at the extremity of the digit impression in the same direction (compared to the track axis). Although there is a degree of rotation of the LPP-IC-0232 track (figure 2), it differs from rotated theropod footprints from the Botucatu Formation by the absence of displacement of the digit ends and by the low degree of sand displacement pattern; differing from the preservational pattern of large autopodium rotation as seen in Fernandes et al. (2024, figure 4.6). We exclude the possibility that LPP-IC-0232 is an anomalous track preservation represented by the rotation of a theropod foot during locomotion; therefore representing a morphology of the trackproducer (figure 2) that differs from theropod tracks of the Botucatu Formation (see Fernandes et al. 2024, Leonardi et al. 2024). Fernandes et al. (2024) observed in LPP-IC-0232 that there is no evidence of internal or external rotation, at least of the digits here interpreted as I and III; thus, as explained previously, the small rotation observed in the track (Figure 2) may have been explained by the hand resting on the substrate in two movements.

Figure 3
Graphs of bivariate and multivariate analyses. (a) linear regression considering the variables: length of the manus imprint vs. length of pes imprint, (b) linear regression considering the variables: width of manus imprint vs. width of pes imprint, (c) morphospace generated with Principal Component analysis taking into account eight metric variables, (d) ternary graph considering the ratios: length of pes/width of pes, length of manus/width of manus, and length of digits/length of metatarsals.

Figure 4
Comparison of pterosaur manus and pes skeletons (based on Tupandactylus – Beccari et al. 2021) with the tracks of Pteraichnus isp. (a) Manus track (LPP-IC-0232) digital model, drawing, and digital skeleton, (b) Pes track (LPP-IC-0233) digital model, drawing, and digital skeleton. In (a) the arrows indicate the position and relative extent of the claw traces (osteological 3D models made by Hugo Cafasso).

Furthermore, as demonstrated by Lallensack et al. (2022), some very elongated dinosaur tracks have been classified as “plantigrade” based on preservational artifacts; they reflect a production mechanism rather than autopodial morphology. Two of these mechanisms are highlighted: (1) penetrative track – sinking of the foot into the soft substrate deeply, leaving a narrow, elongated trace, and (2) slidemark – displacement of the track edge (with or without substrate displacements), mainly anterior and with an indistinct posterior margin, the posterior part of the tracks are usually broad and curved (see Lallensack et al. 2022). We exclude the possibility that LPP-IC-0233 is a result of processes (1) and (2) as follows. Elongated theropod tracks generally do not preserve digits, or preserve only their relative positions in a generally “Y-shaped” trace (with the digital region equal to or slightly smaller than the posterior footprint groove); penetrative tracks often preserved the digit I impressed in theropod tracks, positioned anterior to the posterior margin of tracks that are generally poorly preserved (see Lallensack et al. 2022). In LPP-IC-0233, the digits are relatively well preserved with the presence of pads on the median digit, with all digits positioned anteriorly (Figure 2), differing from the “Y-shaped” pattern of theropods, with sometimes long digit impressions (Lallensack et al. 2022, figure 2). Moreover, the posterior margin of the LPP-IC-0233 track is well preserved, delimiting the foot margin, and the midfoot curve impression is higher than the central groove (figure 2e, f), while penetrative footprints, when curved, appear to have no distinction in height (i.e., they are flat).

Finally, there is no evidence that the track is related to a penetrative track (see Lallensack et al. 2022) due to the depth of the track and the presence of the most well-preserved track edges (Figure 2). Besides that, the digital region in LPP-IC-0233 track is also disproportionate in length when compared to the penetrative track impressions described in Lallensack et al. (2022), and lacks any sand displacements that indicate any sign of “foot sliding” impression (see Fernandes et al. 2024); therefore, the sand displacements observed in LPP-IC-0233 are representative of the expected movement of a plantigrade when walking on a steep dune.

Figure 5
Paleoartistic reconstruction of the environmental scenario of the Botucatu Paleodesert during the Lower Cretaceous, including the trackmaker of Pteraichnus. The fossil tracks are represented by the 3D digital models of the tracks described in this work, which belonged to a pterosaur with a hip height equivalent to 59.71 cm (Paleoart by Hugo Cafasso).

Hip height estimation and size comparisons

Size can serve as an ichnotaxobase only in a limited context (see Bertling et al. 2022, Lallensack et al. 2025), but only when there are significant differences in magnitude. In general, most pterosaur tracks that are assigned to Pteraichnus are small, having a footprint (manus and pes) length <10 cm (Lockley et al. 2008); including Pt. saltwashensis (8.76 cm), Pt. stokesi (9 cm), Pt. dongyangensis (9 cm), Pt. koreanensis (2.57 cm), Pt. gracilis (2.72 cm), and Pt. nipponensis (1.94 cm; see Table I and Li et al. 2021). However, some medium-sized forms like Pt. junggarensis from China (10.25 cm), Pt. palacieisaenzi from Spain (15.34 cm), Pt. yanguoxiaensis from China (12.3 cm), and Pteraichnus isp. from the Argentina, China, United States, and Mexico (varying from 11 cm to 18 cm) are also known (Rodríguez-de La Rosa 2003, Fiorillo et al. 2009, Lee et al. 2008, 2010, Pascual-Arribas et al. 2014, Ha et al. 2022, Heredia et al. 2024, Li et al. 2024). Compared to the above, the materials described here (LPP-IC-0232 and LPP-IC-0233) fall as a medium- to large-sized ichnotaxon (18.2 cm), resembling Pt. palacieisaenzi and Pteraichnus isp. from the United States, and the non-Pteraichnus pterosaur Pu. pentadactylus (Fiorillo et al. 2009, Pascual-Arribas et al. 2014, Lockley et al. 2008, Li et al. 2021); therefore, LPP-IC-0232 and LPP-IC-0233 is related to one of the largest Pteraichnus known to date.

Based on the bivariate models comparing the length of manus imprint versus the length of pes imprint, and width of manus imprint versus the width of pes imprint, it is possible to note a clear correlation between these two metrics (Lm versus Lp – R2 = 0.93885, and Wm versus Wp – R2 = 0.86441); thus generating equations that allow predicting missing length and/or width metrics in pterosaur footprints (figure 3a,b). In both analyses, the materials described here LPP-IC-0232 and LPP-IC-0233 retain higher values within Pteraichnus, corresponding mainly to Pt. palacieisaenzi (figure 3a, b), also confirmed by the PCA analysis (figure 3c). In addition to these, based on the ternary plot, it is possible to note that the values of Ld/Lmt and Lp/Wp are lower and higher in LPP-IC-0233, respectively (figure 3d).

Using equation (1) provided by Li et al. (2024), the estimated hip height of the producer of the tracks described in this work is approximately 59.72 cm. This value is expected, given that LPP-IC-0232 and LPP-IC-0233 are potentially the largest Pteraichnus known to date (rivaling in size Pu. pentadactylus). Furthermore, calculating hip height in various Pteraichnus (based on the original literature and/or Li et al. (2021) and using the equation (1) from Li et al. 2024), we have the following increasing range of hip height (hh): Pt. nipponensis (7.68 cm), Pt. koreanensis (9.7 cm), Pt. gracilis (10.37 cm), Pt. wuerhoensis (14 cm – Li et al. 2024), Pt. saltwashensis (29.51 cm), Pt. stokesi (30.27 cm), Pt. dongyangensis (30.27 cm), Pt. junggarensis (33 cm – Li et al. 2024), Pt. yanguoxiaensis (40.83 cm), Pt. palacieisaenzi (50.56 cm), and the materials described here LPP-IC-0232 and LPP-IC-0233 (59.72 cm). These results confirm that most of the Pteraichnus are small (Lockley et al. 2008), although larger forms have been discovered recently (e.g. Pascual-Arribas et al. 2014, Heredia et al. 2024, this work).

Comments on the trackmaker

The footprint fossil record of pterosaur is distributed globally in the Cretaceous, except in Antarctica and Australia; in the Southern Hemisphere these records are considerably scarce even with the Argentine findings (Calvo & Lockley 2001, Lockley et al. 2008). Thus, in South America, the discoveries from Argentina have provided very important insights into this limited ichnological fossil record (e.g. Calvo & Lockley 2001, Díaz-Martínez et al. 2022, Heredia et al. 2024). Therefore, the new materials described here increase our knowledge and the geographic distribution of these records and although being the first records from Brazil, were expected, since the occurrence of pterosaurs is particularly rich in this country (Martill et al. 2007, Pentland & Poropat 2023) as bellow.

The fossil record of pterosaurs in Brazil is abundant, demonstrating a high diversity of pterodactyloids that are usually found well preserved (Beccari et al. 2021, Pentland & Poropat 2023). Most of the pterosaur body fossil record derives from the Lower Cretaceous of the Araripe Basin, including the genera Anhanguera (Campos & Kellner 1985, Kellner & Tomida 2000, Pinheiro & Rodrigues 2017), Cearadactylus (Leonardi & Borgomanero 1985); Tapejara (Kellner 1989, Eck et al. 2011), Thalassodromeus (Kellner & Campos 2002, Pêgas et al. 2018), Tropeognathus (Kellner et al. 2013), and Tupuxuara (Kellner & Campos 1998, Martill & Naish 2006) from the Romualdo Formation; in addition to Aymberedactylus (Pêgas et al. 2016) and Tupandactylus (Frey et al. 2003, Pinheiro et al. 2011, Beccari et al. 2021) from the Crato Formation – both formations being considered Lagerstätten of the Santana Group in northeastern Brazil (Pentland & Poropat 2023). However, another region of the Lower Cretaceous that stands out in pterosaur occurrences is the Caiuá Group, in the southern portion of Brazil, more specifically due to the taphocenosis known as “Pterosaur Graveyard” (Base of the Goio-Erê Formation – Kellner et al. 2019). From this locality, hundreds of tapejarid individuals derive, including Caiuajara (Manzig et al. 2014, Canejo et al. 2022) and Torukjara (Pêgas 2024) forming the clade Caiuajarina (sensu Pêgas 2024); in addition to the azhdarchoid Keresdrakon (Kellner et al. 2019); exemplifying the cooccurrences of pterosaurs in a desert paleoenvironment (Pêgas 2024). It is relevant to note that the Caiuá Group in Brazil represents an arid to semi-arid paleoenvironment from the Cretaceous, characterized by extensive eolian sandstones deposited in a vast desert system with dunes, interdunes, and ephemeral fluvial environments, that could be analogous to some deposits of the Lower Cretaceous Botucatu Formation.

When comparing the footprints described here with the autopodial morphology of potential producers, the most plausible explanation is that the producer of Pteraichnus isp. from Botucatu Formation (LPP-IC-0232 and LPP-IC-0233) was a later-diverging pterodactyloid. Furthermore, both tracks resemble the azhdarchoid pterosaurs (sensu Andres et al. 2014), likely a form similar to Sinopterus (e.g. Zhang et al. 2019), Tupuxuara (e.g. Peters 2011), Noripterus (e.g. Hone et al. 2018) or Tupandactylus (e.g. Beccari et al. 2021) due to the parallel, subretangular, and proportionally larger metatarsals, differing from Anhanguera, for example (Peters 2011). Peters (2011) suggests that pterosaur tracks have sufficient characteristics to allow their association with the trackmaker, as applied in recent studies (e.g. Li et al. 2024). Thus, based on the similarities, we infer that the trackmaker of LPP-IC-0232 and LPP-IC-0233 could be an azhdarchoid pterosaur due to the similarities of the tracks and the autopodial morphology of taxa such as Noripterus and Tupandactylus, as below.

Based on Beccari et al.’s (2021) description of a complete and undistorted left pes and manus of a Tupandactylus specimen, we developed a 3D osteological model that allowed better comparisons between producer and footprint morphology (figure 4). Tupandactylus navigans Frey et al. (2003) resembles the producer of Pteraichnus isp. from Botucatu Formation in the morphology of the manus, including the digits and unguals and the individual proportionality of each digit when compared to the track LPP-IC-0232 (figure 4a). The similarity of the pes is due to the elongated metatarsals, being the most medial curved and the most lateral straight, and the presence of shortened unguals that can be related to the track LPP-IC-0233 production (figure 4b). Although T. navigans (and later-diverging pterodactyloids – Peters 2011, Beccari et al. 2021) have four pedal digits, in LPP-IC-0233 three demarcated digits are noted, which may represent the marking of two digits in the same location as previously commented (exemplified in the figure 4b). Thus, based strictly on the autopodial morphology [especially of Tupandactylus], we infer that the trackproducer of Pteraichnus isp. described here would tentatively be an azhdarchoid pterosaur or any form more closely related to Tupandactylus.

Implications for the paleoecology of the Botucatu Paleodesert

Even a single isolated track, or a few tracks, can add valuable biological information about the distribution and ecology of a particular taxon or clade (Falkingham 2014, Leonardi et al. 2024). Furthermore, given the fact that footprint morphology is determined by limb movement, autopodial anatomy, as well as substrate characteristics and consistency; general studies of fossil footprints/trackways can provide useful insights into the trackmaker including their behavior and paleoenvironment (Fernandes & Carvalho 2008, Falkingham 2014, Leonardi et al. 2024). Thus, the discovery of Pteraichnus isp. represents the first occurrence of a pterosaur footprint in the Botucatu Formation, increasing our knowledge about the diversity of tetrapods in the desert environments of the Early Cretaceous of the Botucatu Paleodesert.

According to Calvo & Lockley (2001), later demonstrated in other studies (e.g. Hwang et al. 2002, Xing et al. 2012, 2023, Chen et al. 2013, Díaz-Martínez et al. 2022), there is an association of pterosaur tracks and different types of dinosaurs and bird in some ichnocenoses, especially from the Cretaceous. This same association, pterosaurs and dinosaurs, can be observed in the Botucatu Paleodesert based on the occurrence of Pteraichnus isp. and other taxa including tridactyl dinosaurs (ornithischians and theropods), small mammals, and lizards (Leonardi 1994, Fernandes & Carvalho 2007, Buck et al. 2017a, 2022, Fernandes et al. 2024, Leonardi et al. 2024). Moreover, as previously mentioned, in desert environments of the Goio-Erê Formation, the tapejarid pterosaurs Caiuajara and Torukjara, and the azhdarchoid Keresdrakon were recorded, in addition to noasaurid theropods; ichnofossils of mammals and theropods are also known, exemplifying the coexistence of these faunas (Leonardi 1977, 1994, Manzig et al. 2014, Kellner et al. 2019, Langer et al. 2019, Souza et al. 2021, Pêgas 2024). Thus, exemplifying the faunal similarity in the arid environments of the Paraná Basin based on the fossil occurrences of the Caiuá Group and ichnofossils of the Botucatu Formation.

Assuming an attribution to azhdarchoid pterosaur as producer of Pteraichnus isp. from the Botucatu Paleodesert (based on the morphology of the footprints and the autopodial osteology of Tupandactylus as explained; figure 4), it can be assumed that it would be an animal with an herbivorous feeding strategy, probably of hard-plants such as hard fruits, roots and leaves as suggested to tapejarids in general (Wellnhofer & Kellner 1991, Kellner et al. 2019, Pêgas et al. 2021). However, as proposed for Keresdrakon, a desert-dwelling azhdarchoid pterosaur, it could have represented a predator of small lizards, eggs, other small pterosaurs, or carcasses (Kellner et al. 2019). Thus, the track producer of Pteraichnus isp. described here could, potentially, make forays into the desert since they had several terrestrial abilities that, as suggested by Smyth et al. (2024), facilitated feeding ecologies as well as the increase in their body size. Based on this, the producer of the tracks could have been a desert opportunist (figure 5).

Finally, the records of Pteraichnus LPP-IC-0232 and LPP-IC-0233 represent specimens of the same age and/or size, giving us evidence of a probable single individual (correlation in figure 4a), or at least two individuals of proportionally similar size. This differs from the theropod producer of Farlowichnus, for example, which has traces of several ontogenetic stages preserved in rocks from the Botucatu Formation (Leonardi et al. 2024). In other studies (e.g. Jung et al. 2022), multiple Pteraichnus isp. tracks from Korea with different sizes indicate gregarious behavior of pterosaurs of different ages; more findings from Botucatu Formation will likely shed light on this issue.

CONCLUSIONS

Pterosaurs were very abundant animals in the supercontinent Gondwana, especially during the Cretaceous, and are well-represented in Brazil. However, the ichnological record of this group remains poorly documented. In South America, footprints and trackways had only been recorded in Argentina (e.g. Calvo & Lockley 2001, Heredia et al. 2024) – therefore, the new materials described here, Pteraichnus isp. LPP-IC-0232 and LPP-IC-0233, from the Lower Cretaceous Botucatu Formation (Paraná Basin) carry historical value and expands the biogeography of this ichnogenus. These finds also increase our knowledge about the fossil record of Brazil, being these the first records of pterosaur fossil tracks. The recognition of pterosaurs tracks in the Botucatu Formation increases the known ichnofaunal diversity, adding more complexity to the paleoecological webs of this desert paleoenvironment.

Acknowledgements

We would like to thank Luciana B. dos Reis Fernandes (UFSCar) for her help in collecting the materials, Gabriel E. B. de Barros (UFSCar) for several comments made throughout the construction of this study, Camila B. Pinto Lacerda (UNESP) for her help editing figures, and Hugo Cafasso (Yvy figures) for the art of figure 5, as well as his help in the virtual comparison stages (3D modeling) of the studied materials (exemplified in figure 4). We are also grateful to Juliana M. Sayão (MN/UFRJ) for the invitation to submit this work to the special issue dedicated to pterosaurs. We thank MorphoSource for being a repository where the 3D models of the footprints were deposited. This study was financed, in part, by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil; Process #2024/08798-6 (grant to MBSL).

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Publication Dates

• Publication in this collection
  15 Sept 2025
• Date of issue
  2025

History

• Received
  20 Dec 2024
• Accepted
  21 May 2025