New plant fossils from the Lower Cretaceous of the Parnaíba Basin, Northeastern Brazil: Southern Laurasia links

This study reports on the presence of a diverse set of gymnosperm and angiosperm macrofossils from the Codó Formation, Parnaíba Basin, whose assemblage was previously known only by the occurrence of pollen grains, spores, wood fragments, leaves and roots associated with Nympheaceae. In the Brejo municipality, northeastern Maranhão State, marl levels attest a transitional to marginal lacustrine environment, with occasional marine ingressions, demonstrated by the presence of crustaceans, gastropods and fishes. The plant fossils are preserved exclusively by molds and impressions, and its diversity is represented by few specimens, suggesting taphonomic processes of selection and transportation. The taphoflora is composed of Gnetales (?Drewria), conifers (Cupressinocladus and Brachyphyllum), and basal angiosperms (Nympheales, Magnollids, and/or basal Eudicots), which support an upper Aptian - ?Albian age. It displays affinities with both the well-known flora of the Araripe Basin (Santana Formation) as well as those ones identified in deposits from the south of North America (Potomac Group), suggesting that terrestrial links persisted in the equatorial areas of the Pangea at the end of the Early Cretaceous.

KEYWORDS:
Lower Cretaceous; Macroflora; Parnaíba Basin; Codó Formation

Authorship

Rafael Matos Lindoso ^**Corresponding author.

Instituto Federal de Educação, Ciência e Tecnologia do Maranhão - São Luís (MA), Brazil. E-mail: rafael.lindoso@ifma.edu.brInstituto Federal de Educação, Ciência e Tecnologia do MaranhãoBrazilSão Luís, MA, BrazilInstituto Federal de Educação, Ciência e Tecnologia do Maranhão - São Luís (MA), Brazil. E-mail: rafael.lindoso@ifma.edu.br

Tânia Lindner Dutra

Universidade do Vale do Rio dos Sinos - São Leopoldo (RS), Brazil. E-mail: dutratl@gmail.comUniversidade do Vale do Rio dos SinosBrazilSão Leopoldo, RS, BrazilUniversidade do Vale do Rio dos Sinos - São Leopoldo (RS), Brazil. E-mail: dutratl@gmail.com

Ismar de Souza Carvalho

Departamento de Geologia, Universidade Federal do Rio de Janeiro - Rio de Janeiro (RJ), Brazil. E-mail: ismar@geologia.ufrj.brUniversidade Federal do Rio de JaneiroBrazilRio de Janeiro, RJ, BrazilDepartamento de Geologia, Universidade Federal do Rio de Janeiro - Rio de Janeiro (RJ), Brazil. E-mail: ismar@geologia.ufrj.br

Manuel Alfredo Medeiros

Universidade Federal do Maranhão - São Luís (MA), Brazil. E-mail: manuel.alfredo@ufma.brUniversidade Federal do MaranhãoBrazilSão Luís, MA, BrazilUniversidade Federal do Maranhão - São Luís (MA), Brazil. E-mail: manuel.alfredo@ufma.br

*Corresponding author.

SCIMAGO INSTITUTIONS RANKINGS

Figures

Figures (5)

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Figure 1:
The location is Brejo County, Maranhão State, northeastern Brazil. The black stars indicate the two quarries where the plant fossils were collected.

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Figure 2:
A stratigraphic profile of the Faveirinha Quarry (A) and Perneta Ranch (B), in Brejo City, Maranhão. In (C) and (D) the same outcrops expose the levels of the Codó Formation containing plant fossils.

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Figure 3:
Gnetales (A,B,C) and conifer-related forms (D,E,F) in the Codó Formation flora. (A) Monopodial and trifurcate dichotomous branch, one time irregularly forked, carrying opposite, oblong leaves, comparable to those associate of the reproductive structure of Drewria potomacencis Crane and Upchurch (UFRJ-DG1444-Pb); (B) outline of the shoot in A, showing the fine details of venation with probable apically orientated chevrons (arrow); (C) detail of the axillary branch venation; (D) Cupressinocladus sp. (UFRJ-DG1987-Pb), branch impression with sub-opposite spreading bifacial, cushion-like and keeled leaves; (E) cf. Brachyphyllum sp. (UFRJ-DG1988-Pb), impression of an apical branch and of the sub-alternate to opposite second order branches; (F) detail of E, highlighting the apical contours of the spirally disposed leaves and their radial striations. Figures 3C and 3F are detailed reproductions of the figures 3A and 3E, respectively. Scale bars: 1 cm.

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Figure 4:
CF1 holomorphotype (UFRJ-DG 1457a-1457b Pb). (A, B) Mold and cast (mineralized) of a trilobed “birdfoot”-like leaf. The white arrow in B points to probable aligned stomata or glands over the central lobe. The black one indicates the fine marginal vein; (C) drawing of B, highlighting the weak visible secondary and marginal veins; (D, E) additional related leaf fragments, with partial axes and basal leaf impressions (UFRJ-DG 1983, 1994 Pb); (F) A folded leafy shoot showing an apparent additional unilobed leaf (UFRJ-DG 1986 Pb). Scale bars = 1 cm, except in figure F = 0.5 cm.

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Figure 5:
(A, B) CF2 morphotype. A. reniform leaf (UFRJ-DG 1985-Pb) eccentrically inserted in a slender petiole and covered by dehydrated coats of iron minerals. Black arrows point to the weakly preserved triangular teeth more visible in the middle part of the margin. White arrows indicate the poorly developed (or preserved) nodes or grooves along the axes; (B) part of an associated axis with a short-ramified shoot (UFRJDG1984-Pb). Delicate striations over it could indicate a nodular character or the presence of aerenchymatous tissues; (C-E) CF3 morphotype (UFRJ-DG 1800-Pb), showing partially preserved pinnatilobed leaf, with decurrent lateral lobes of entire margins; (D) outline of C, highlighting the pinnate main vein and the irregular pattern of the secondary veins (semicraspedodromous?); (E) an additional cast of an incomplete fragment, showing the long and well-preserved swollen petiolate base (UFRJ-DG 1990-Pb). Scale bar = 1 cm.

Figure 1: The location is Brejo County, Maranhão State, northeastern Brazil. The black stars indicate the two quarries where the plant fossils were collected.

Figure 2: A stratigraphic profile of the Faveirinha Quarry (A) and Perneta Ranch (B), in Brejo City, Maranhão. In (C) and (D) the same outcrops expose the levels of the Codó Formation containing plant fossils.

Figure 3: Gnetales (A,B,C) and conifer-related forms (D,E,F) in the Codó Formation flora. (A) Monopodial and trifurcate dichotomous branch, one time irregularly forked, carrying opposite, oblong leaves, comparable to those associate of the reproductive structure of Drewria potomacencis Crane and Upchurch (UFRJ-DG1444-Pb); (B) outline of the shoot in A, showing the fine details of venation with probable apically orientated chevrons (arrow); (C) detail of the axillary branch venation; (D) Cupressinocladus sp. (UFRJ-DG1987-Pb), branch impression with sub-opposite spreading bifacial, cushion-like and keeled leaves; (E) cf. Brachyphyllum sp. (UFRJ-DG1988-Pb), impression of an apical branch and of the sub-alternate to opposite second order branches; (F) detail of E, highlighting the apical contours of the spirally disposed leaves and their radial striations. Figures 3C and 3F are detailed reproductions of the figures 3A and 3E, respectively. Scale bars: 1 cm.

Figure 4: CF1 holomorphotype (UFRJ-DG 1457a-1457b Pb). (A, B) Mold and cast (mineralized) of a trilobed “birdfoot”-like leaf. The white arrow in B points to probable aligned stomata or glands over the central lobe. The black one indicates the fine marginal vein; (C) drawing of B, highlighting the weak visible secondary and marginal veins; (D, E) additional related leaf fragments, with partial axes and basal leaf impressions (UFRJ-DG 1983, 1994 Pb); (F) A folded leafy shoot showing an apparent additional unilobed leaf (UFRJ-DG 1986 Pb). Scale bars = 1 cm, except in figure F = 0.5 cm.

Figure 5: (A, B) CF2 morphotype. A. reniform leaf (UFRJ-DG 1985-Pb) eccentrically inserted in a slender petiole and covered by dehydrated coats of iron minerals. Black arrows point to the weakly preserved triangular teeth more visible in the middle part of the margin. White arrows indicate the poorly developed (or preserved) nodes or grooves along the axes; (B) part of an associated axis with a short-ramified shoot (UFRJDG1984-Pb). Delicate striations over it could indicate a nodular character or the presence of aerenchymatous tissues; (C-E) CF3 morphotype (UFRJ-DG 1800-Pb), showing partially preserved pinnatilobed leaf, with decurrent lateral lobes of entire margins; (D) outline of C, highlighting the pinnate main vein and the irregular pattern of the secondary veins (semicraspedodromous?); (E) an additional cast of an incomplete fragment, showing the long and well-preserved swollen petiolate base (UFRJ-DG 1990-Pb). Scale bar = 1 cm.

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New plant fossils from the Lower Cretaceous of the Parnaíba Basin, Northeastern Brazil: Southern Laurasia links

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[1] *Corresponding author.