New dyrosaurid remains (Crocodyliformes, Mesoeucrocodylia) from the Paleocene of the Paraíba Basin, NE Brazil

Abstract

-The fossil crocodyliforms from the Paraíba Basin in Northeastern Brazil are represented by two species, Hyposaurus derbianus, (uncertain age) and Guarinisuchus munizi, from the Paleocene Maria Farinha Formation. Herein we present new material of a dyrosaurid also collected in deposits of the Maria Farinha Formation, representing cranial, axial and appendicular remains. The specimens are housed at Centro Acadêmico de Vitória, Universidade Federal de Pernambuco (CAV-UFPE) and at Universidade Federal Rural de Pernambuco (UFRPE). The most important contribution of this find is a well-preserved mandibular specimen (CAV 0056-V) with 16 alveoli on the left side and 13 on the right side. Nine complete or partial tooth crowns are preserved, in positions 1-5. The teeth are conical and homodont with vertical striations. The largest teeth are located at positions d1 and d4. The biggest occlusion pits are located between positions d2 and d3. The seventh alveoli are reduced and close to the eighth alveoli. The mandible, CAV 0056-V, possesses three foramina in the anterior portion of the dentaries and the mandibular symphysis extends to the posterior margins of the d11-d12 dentary alveoli. Based on the features presented in the mandible and the other fossils recovered, we attribute these materials to Dyrosauridae, particularly, to Guarinisuchus cf. G. munizi. Key words:Crocodyliformes, Dyrosauridae, NE Brazil, Paleocene, Paraíba Basin. RESUMO -Os Crocodyliformes fósseis da Bacia da Paraíba, Nordeste brasileiro, são representados por duas espécies, Hyposaurus derbianus de idade incerta e Guarinisuchus munizi, dos estratos paleocênicos da Formação Maria Farinha. Aqui são apresentados novos materiais de dyrossaurídeo da Formação Maria Farinha, representados por fragmentos craniais, axiais e apendiculares. Os espécimes estão armazenados no Centro Acadêmico de Vitória da Universidade Federal de Pernambuco (CAV-UFPE) e na Universidade Federal Rural de Pernambuco (UFRPE). O novo material contém uma mandíbula bem preservada (CAV 0056-V), com 16 alvéolos do lado esquerdo e 13 do lado direito. Nove coroas dentárias estão preservadas total ou parcialmente completas, nas posições 1-5. Os dentes são homodontes com forma cônica e estrias verticais. Os dentes de maior comprimento estão localizados nas posições d1 e d4. As maiores marcas de oclusão ocorrem entre as posições d2 e d3. Os alvéolos d7 apresentam dimensões reduzidas e ocorrem próximos aos alvéolos d8. A mandíbula, CAV 0056-V apresenta três forames na porção anterior dos dentários e a sínfise mandibular estende-se até a borda posterior dos alvéolos dentários d11-d12. Portanto, fundamentado nas características apresentadas na mandíbula e pelos outros espécimes, nós associamos estes materiais à Dyrosauridae, particularmente, Guarinisuchus cf. G. munizi.

A dyrosaurid from the Paleocene of Senegal

“…Although these features are present in Alligator too, they are not as marked. Overall, the tibia of MHNT.PAL.2012.0.45 is similar to other tibia described for dyrosaurids (Langston, 1995; Schwarz et al, 2006; Sena et al, 2017).…”

“…A 9 mm long ovoid depression is observed on the anterolateral corner of the tibia (Fig. 6.8), as previously observed in the tibia of Guarinisuchus munizi Barbosa, Kellner, and Viana, 2008 (Sena et al, 2017, fig. 3M).…”

“…A flattened femur is known for Acherontisuchus guajiraensis Hastings, Bloch, and Jaramillo, 2011, for which “the fourth trochanter is especially large for the family and the paratrochanteric fossa is deeper than the shallow pit seen in Congosaurus bequaerti ” (Hastings et al, 2011, p. 1106). Sena et al (2017) described the proximal portion of a right femur for Guarinisuchus munizi . A right dyrosaurid femur was described by Arambourg (1952), who noticed that the proximal head is in line with the distal condyles (Arambourg, 1952, fig.…”

“…Reports from the Danian of Brazil including Hyposaurus derbianus (Cope, 1886) concerned fragmentary specimens from the Maria Farinha Formation (see review in Hastings et al, 2010). Guarinisuchus munizi is known from a complete skull and few postcranial elements, also from the Maria Farinha Formation of Brazil (Barbosa et al, 2008) and recently, other mandibular and cranial remains have been assigned to this species (Sena et al, 2017).…”

The postcranial skeleton of Cerrejonisuchus improcerus (Crocodyliformes: Dyrosauridae) and the unusual anatomy of dyrosaurids

“…Dyrosaurid remains have been found both in marine ( Buffetaut, 1976 , 1978a ; Jouve et al, 2005 , 2006 ; Schwarz, Frey & Martin, 2006 ; Barbosa, Kellner & Viana, 2008 ; Jouve et al, 2008 ; Schwarz-Wings, Frey & Martin, 2009 ; Shiller, Porras-Muzquiz & Lehman, 2016 ; Sena et al, 2017 ; Martin, Sarr & Hautier, 2019 ; de Souza et al, 2019 ; Jouve & Jalil, 2020 ) and freshwater ( Buffetaut, 1978a ; Khosla et al, 2009 ; Hastings, Bloch & Jaramillo, 2011 ; Hastings, Bloch & Jaramillo, 2014 ; de Souza et al, 2019 ) deposits, and are usually pictured as large ‘crocodiles’ ( Buffetaut, 1976 , 1978a , 1980 ; Langston, 1995 , Schwarz-Wings, Frey & Martin, 2009 ), although some taxa were fairly small (≤3 m) ( Jouve, Bouya & Amaghzaz, 2005 ; Hastings et al, 2010 ; Hastings, Bloch & Jaramillo, 2014 ). The relative importance of fossils in marine deposits suggests that dyrosaurids mainly thrived in coastal environments ( Troxell, 1925 ; Buffetaut, 1976 ; Denton, Dobie & Parris, 1997 ; Jouve et al, 2006 ; Schwarz, Frey & Martin, 2006 ; Jouve et al, 2005 ; Barbosa, Kellner & Viana, 2008 ; Jouve et al, 2008 , Salih et al, 2015 ; Shiller, Porras-Muzquiz & Lehman, 2016 ; Sena et al, 2017 ; Martin, Sarr & Hautier, 2019 ; Jouve & Jalil, 2020 ); two lineages from South America ( Cerrejonisuchus–Anthracosuchus , and Acherontisuchus ) likely inhabited freshwater environments ( Hastings, Bloch & Jaramillo, 2011 , 2014 ; Wilberg, Turner & Brochu, 2019 ), whereas other freshwater dyrosaurids have also been found in Asia ( Buffetaut, 1978a ) and India ( Khosla et al, 2009 ). Yet, ’marine dyrosaurids’ may have actually inhabited both environments during their lifespan, with youngs living in freshwater environments and adults transitioning to t...…”