Paleocene resurrection of a crocodylomorph taxon: Biotic crises, climatic and sea level fluctuations

Abstract

Postcranial material of a crocodylomorph from the Danian of Oulad Abdoun Basin (Morocco) is described. Several characters, in particular the shape of its dorsal osteoderms, allows its attribution to Pholidosauridae.Up till now, the latest known pholidosaurid was Terminonaris, from the Early Turonian of North America, so, the Moroccan pholidosaurid extends the stratigraphic range of the group to more than 20 million years younger, and shows that the pholidosaurids survived the K-Pg crisis. The reevaluation and the phylogenetic analysis of Dakotasuchus kingi, Woodbinesuchus byersmauricei, and Sabinosuchus coahuilensis, previously considered as goniopholidids and dyrosaurid, respectively, revealed rather that they are pholidosaurids. This analysis also suggests that at least two independent pholidosaurid lineages reached the Maastrichtian, among which one crossed the K-Pg boundary. This study proposes the first analysis of tethysuchian diversity from the Late Jurassic to the Early Paleogene. Two diversity peaks are observed during the Oxfordian and Cenomanian, two stages of high paleotemperatures evaluated with the δ 18 O. The tethysuchian diversity strongly decreases after the Cenomanian, a decline that may be correlated with the "Ocean Anoxic Event" (OAE 2), which caused the strong marine faunal turnover during the Cenomanian-Turonian time interval. The large Turonian-Coniacian oceanic regression could also be a factor in the tethysuchian decline. After that, tethysuchian diversity remains low until the Maastrichtian-lower Paleocene marine tethysuchian dyrosaurid diversification, correlated with the Late Cretaceous-Paleocene 3 transgression. At least one pholidosaurid lineage crossed the K-Pg boundary, confirming the weak impact of this crisis on the crocodylomorphs. Pholidosaurids seem to go extinct at the beginning of the Paleocene, possibly due to the strong radiation of dyrosaurids in marine environments and crocodylians in fresh-water during this time period.

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

“…Yet, our analysis of craniodental morphological data (Fig. SI 1 in Supplemental Information) splits the Hyposaurine cluster of Schwarz-Wings, Frey & Martin (2009), and places Congosaurus close to Dyrosaurus instead, which complies with the results of Jouve & Jalil (2020). The postcranial-restricted PCoA (Fig.…”

“…Dyrosauridae is an extinct family of neosuchian crocodyliforms that is first recorded in the Campanian–Maastrichtian Shendi Formation of Sudan ( Salih et al, 2015 ). Dyrosaurids survived the Cretaceous–Paleogene mass extinction ( Bronzati, Montefeltro & Langer, 2012 , 2015 ; Hastings, Bloch & Jaramillo, 2014 ; Wilberg, Turner & Brochu, 2019 ; Jouve & Jalil, 2020 ), and disappeared during the Eocene (presumably at the Ypresian–Lutecian boundary) ( Buffetaut, 1978a ; Jouve et al, 2006 ; Jouve, 2007 ; Martin, Sarr & Hautier, 2019 ). The origin of dyrosaurids is placed in Africa ( Barbosa, Kellner & Viana, 2008 ; Jouve, Bouya & Amaghzaz, 2008 ; Hastings, Bloch & Jaramillo, 2014 ; Jouve et al, 2020 ), with their apparition dating from the Late Cretaceous ( Hastings, Bloch & Jaramillo, 2014 ; Jouve et al, 2020 ).…”

“…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...…”

“…marine, freshwater, terrestrial) ( Hastings, Bloch & Jaramillo, 2014 ; Wilberg, Turner & Brochu, 2019 ). More recently, postcranial remains have started to show their importance in dyrosaurids ( Langston, 1995 ; Jouve & Schwarz, 2004 ; Schwarz, Frey & Martin, 2006 ; Schwarz-Wings, Frey & Martin, 2009 ; Martin, Sarr & Hautier, 2019 ; de Souza et al, 2019 ; Jouve & Jalil, 2020 ; Jouve et al, 2020 ), notably for systematics ( Langston, 1995 ; de Souza et al, 2019 ; Jouve & Jalil, 2020 ; Jouve et al, 2020 ) and ecological inferences ( Jouve & Schwarz, 2004 ; Schwarz, Frey & Martin, 2006 ; Schwarz-Wings, Frey & Martin, 2009 ; Martin, Sarr & Hautier, 2019 ).…”

Ecological opportunity and the rise and fall of crocodylomorph evolutionary innovation

“…B 288: 20210069 Cenozoic (80-60 Ma), following 100 million years of slow to moderate rates in other tethysuchians (figures 3c,d). Dyrosaurids achieved great diversity during this turbulent interval [69], when other competing marine reptile groups became either less diverse in the latest Cretaceous (e.g. polycotylid plesiosaurs) or extinct at the K-Pg mass extinction event (all plesiosaurs and mosasaurs).…”