Mariliasuchus
Encyclopedia
Mariliasuchus is an extinct genus
of Late Cretaceous
notosuchia
n mesoeucrocodylia
n found near Marilia
, Brazil
. It was described in 1999 by Brazilian palaeontologists Ismar de Souza Carvalho and Reinaldo J. Bertini.
Its type species is M. amarali, in honour of Sérgio Estanislaw do Amaral, Brazilian naturalist
. A second species, M. robustus, was named in 2007.
All of these specimens have been recovered in a road cut near the town of Marilia. They come from the upper part of the Adamantina Formation
, indicating a Late Cretaceous (possibly Campanian/Maastrichtian) age.
. Andrade et al. (2006), while studying the palate and choanae of some mesoeucrocodylians, reached this same conclusion. Though no name was given to this clade in either publication, it is referred in this article as Comahuesuchidae
.
Mariliasuchus, unlike modern crocodylians, was an animal of terrestrial habits. Its nostrils were located on the front of the skull, unlike modern crocodiles, in which the nostrils face upwards, to help the animal breathe while its almost completely submerged. Furthermore, the eyes in M. amarali are faced laterally (in modern crocodiles they face upwards). It had a very modified dentition, differentiated in incisiforms, caniforms and molariforms. Strangelly, in particular, were the anterior-most teeth, which were directed horizontally rather than vertically. The function of this strange arrangement is not yet clear, but Vasconcellos et al. (2002) made comparisons with the dentition of pigs
, indicating that their dietary preferences may be convergent. It also had strong jaw muscles, indicating a good degree of mandibular activity.
There seems to be a significant degree of variation between specimens of M. amarali. Some of this is related to ontogenetic variation, but some may also suggest sexual dimorphism, or even that some of the specimens assigned to this species belong to a different animal.
Ontogenetic studies done by Vasconcellos and Carvalho (2005) concluded that during its growth, the skull of M. amarali individuals becomes shorter and the skull more resistant, while being laterally compressed. In adulthood, the orbit has a less circular arrangement than in younger individuals.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
notosuchia
Notosuchia
Notosuchia is a suborder of primarily Gondwanan mesoeucrocodylian crocodylomorphs that lived during the Cretaceous. Fossils have been found from South America, Africa, and Asia...
n mesoeucrocodylia
Mesoeucrocodylia
Mesoeucrocodylia is the name of the clade that includes Eusuchia and the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day....
n found near Marilia
Marília
Marília is a Brazilian city and municipality in the midwestern region of the state of São Paulo. Its distance from the state capital is by highway, by railway and in a straight line. It is located at latitude 22º 12'50 "south and longitude 49º 56'45" west, with an altitude of 675 meters...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. It was described in 1999 by Brazilian palaeontologists Ismar de Souza Carvalho and Reinaldo J. Bertini.
Its type species is M. amarali, in honour of Sérgio Estanislaw do Amaral, Brazilian naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
. A second species, M. robustus, was named in 2007.
Material
Several specimens of M. amarali have been found to date:- UFRJ DG 50-R (holotype): a partially complete and articulated skeleton, including a nearly complete skull and partially preserved axial and appendicular skeletons. It belongs to a juvenile specimen.
- UFRJ DG 105-R
- UFRJ DG 106-R
- MZSP-PV 50
- MZSP-PV 51
- MN 6298-V
- MN 6756-V
All of these specimens have been recovered in a road cut near the town of Marilia. They come from the upper part of the Adamantina Formation
Adamantina Formation
The Adamantina Formation is a geological formation in Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation...
, indicating a Late Cretaceous (possibly Campanian/Maastrichtian) age.
Systematics
A phylogenetic analysis done by Zaher et al. (2006) found Mariliasuchus amarali to share a close relationship with ComahuesuchusComahuesuchus
Comahuesuchus is an extinct genus of notosuchian crocodylomorph from the Late Cretaceous of Argentina. It was described by palaeontologist José Bonaparte in 1991.The type species is C. brachybuccalis.- Material :...
. Andrade et al. (2006), while studying the palate and choanae of some mesoeucrocodylians, reached this same conclusion. Though no name was given to this clade in either publication, it is referred in this article as Comahuesuchidae
Comahuesuchidae
Comahuesuchidae is a family of notosuchian crocodyliforms. Constructed in 1991, it includes the genera Comahuesuchus and Anatosuchus. Among the characteristics that are unique to this family is an external naris that is inset into the tip of the snout. There is also a diastema, or gap between the...
.
Palaeobiology
PIGS
PIGS is a four letter acronym that can stand for:* PIGS , Phosphatidylinositol glycan anchor biosynthesis, class S, a human gene* PIGS , the economies of Portugal, Italy , Greece and Spain...
, indicating that their dietary preferences may be convergent. It also had strong jaw muscles, indicating a good degree of mandibular activity.
There seems to be a significant degree of variation between specimens of M. amarali. Some of this is related to ontogenetic variation, but some may also suggest sexual dimorphism, or even that some of the specimens assigned to this species belong to a different animal.
Ontogenetic studies done by Vasconcellos and Carvalho (2005) concluded that during its growth, the skull of M. amarali individuals becomes shorter and the skull more resistant, while being laterally compressed. In adulthood, the orbit has a less circular arrangement than in younger individuals.