Mariliasuchus: a mammal-like croc

Mariliasuchus amarali (Carvalho and Bertini 1999, Zaher et al. 2006, Nobre et al. 2007) is an Early Cretaceous meso-croc with a short skull and mammal like traits.

Figure 1. Mariliasuchus skull in several views. Note the premaxillaery fangs and the short blunt remainder of the teeth.

Figure 1. Mariliasuchus skull in several views. Note the premaxillaery fangs and the short blunt other teeth. Note the postdentary length of the mandible acting as an anchor for powerful muscles. There’s sort of a double lateral fenestra here, also seen in Baurusuchus. The upper lateral temporal fenestra appears between the quadrate and squamosal. 

Distinct from most crocs,
but like most mammals, Mariliasuchus nostrils faced anteriorly. Like most mammals the teeth were divided into incisors, canines and molars, but the canines were on the premaxilla. The incisors were procumbent. Vasconcellos et al. (2002) compared these with the teeth of pigs. Oral processing of the food was evident by the shape of the teeth, the inset of the maxillary teeth (implying lips) and the ability of the the mandible to move back and forth. The mineral composition of coprolites found with the specimens also indicate an omnivorous diet.

Ontogenetic studies
(Vasconcellos and Carvalho 2005) noted skulls became shorter and laterally compressed during growth — but this could be phylogenetic since Mariliasuchus nests at the base of a narrow-skull clade that includes Caipirasuchus and Baurusuchus in the large reptile tree (Fig. 2) and the skull shown here (Fig. 1) is wider than tall. These sisters of Mariliasuchus likewise have anterior nares and Caipirasuchus has blunt teeth with premaxillary canines.

Figure 2. Mariliasuchus nests at the base of a derived clade of narrow-skulled crocs.

Figure 2. Mariliasuchus nests at the base of a derived clade of narrow-skulled crocs, like its contemporary, Baurusuchus. This is a subset of the large reptile tree. Lewisuchus is a pre-dinosaur.

The postcranial skeleton
includes traits similar to those of Notosuchus and extant crocs. Nobre and Carvalho (2013) thought Mariliasuchus had a sprawling posture like living crocs.

The larger clade that includes Mariliasuchus
also includes the tiny herbivore Simosuchus and that clade is the sister clade to living crocs like Caiman and marine crocs with flippers and tails like Metriorhynchus (Fig. 2).

References
Carvalho IS and Bertini R 1999. Mariliasuchus: um novo Crocodylomorpha (Notosuchia) do Creta´ceo da Bacia Bauru. Geologı´a Colombiana 24: 83–105.
Nobre PH and Souza Carvalho I de 2013. Postcranial skeleton of Mariliasuchus amarali Carvalho and Bertini, 1999 (Mesoeucrocodylia) from the Bauru Basin, Upper Cretaceous of Brazil. Ameghiniana 50 (1): 98–113.
Nobre PH et al. 2007. Mariliasuchus robustus, a new Crocodylomorpha (Mesoeucrocodylia) from the Bauru Basin, Brazil. Anuário do Instituto de Geociências 30 (1): 38–49.
Zaher H et al. 2006. Re-description of the cranial morphology of Mariliasuchus amarali, and its phylogenetic affinities (Crocodyliformes, Notosuchia)”. American Museum Novitates 3512: 1–40.

wiki/Mariliasuchus

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