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Lagosuchus
Fossil range: Middle Triassic

Scientific classification

Class:

Sauropsida

Infraclass:

Archosauromorpha

(Unranked) :

Ornithodira

Family:

Lagosuchidae

Genus:

Lagosuchus

Species:

L. talanpayenisis
Romer, 1972

Lagosuchus was a small archosaur from the Middle Triassic period. It is generally thought to be closely related to dinosaurs, as a member of the Dinosauromorpha.

Lagosuchus was a lightly-built archosaur, and is notable for its long slender legs and well-developed feet - features it shares with certain dinosaurs. These features, along with the shape of its hips, suggest that it could run on its hind legs for short periods, although it probably moved on all fours most of the time. Lagosuchus was likely an agile predator that could use speed to chase its prey and to escape larger predators.[1]

Lagosuchus is regarded by some to be nomen dubium and L. lilloensis has been referred to Marasuchus by Paul Sereno in 1994.

Description[]

Lagosuchus is known from very incomplete remains (only a hind leg plus a shoulder blade and vertebrae can be definitely assigned to it). However, features of the leg show that it was a lightly built archosaur, and is notable for its long slender legs and well-developed feet - features it shares with certain dinosaurs. These features, as well as comparisons to close relatives, suggest that it could run on its hind legs for short periods, although it probably moved on all fours most of the time. Lagosuchus was likely an agile predator that could use speed to chase its prey and to escape larger predators.[1]

Lagosuchus is regarded by some to be nomen dubium and the second species assigned to the genus, L. lilloensis was reclassified as Marasuchus by Paul Sereno in 1994.

History[]

The type species Lagosuchus talampayensis was first described by Alfred S. Romer in 1971, who considered it a "pseudosuchian" (then a collection of various non-dinosaurian "thecodonts"). In 1972 he named a second species, Lagosuchus lilloensis, known from larger and more well-preserved specimens. A later review by Jose Bonaparte in 1975 synonymized the two species and considered Lagosuchus intermediate between "pseudosuchians" and saurischian dinosaurs.

Modern authors now consider at least L. lilloensis to be firmly on the lineage of archosaurs leading to dinosaurs. However, the genus Lagosuchus is regarded by some to be dubious. Paul Sereno and Andrea Arcucci considered L. talampayensis to be undiagnosable in a 1994 study, and reclassified L. lilloensis as a new genus, Marasuchus. In 2019, PULR 09, the holotype skeleton of L. talampayensis, was redescribed by Federico Agnolin and Martin Ezcurra. They argued that the skeleton was not only diagnostic, but indistinguishable from specimens of Marasuchus lilloensis. As a result, they supported the synonymy proposed by Bonaparte, referring specimens of Marasuchus lilloensis back to Lagosuchus talampayensis.

The ChaƱares Formation's age has been through much debate. It has traditionally been considered to belong to the Ladinian stage, the last stage of the Middle Triassic. Radiometric dating in 2016 has dated the main fossiliferous section of the formation to the early Carnian stage, near the start of the Late Triassic.

Paleobiology[]

References[]

  1. ^ Palmer, D., ed (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 97. ISBN 1-84028-152-9.