Desmatosuchus

Meaning: "link crocodile"

Species: "D." haplocerus, D. spurensis, and D. smalli

Nominal Author: Case 1920

Age: Carnian(?)/ Norian (Late Triassic)

Location: Southwestern US (Texas, New Mexico, Arizona - Chinle and Dockum strata)

Physical Characteristics: Large (4+ meters) aetosaur. Typical aetosaur characteristics include an armored carapce arranged in four columns along the dorsal side, an upturned “pig-nosed” premaxilla, and stout forelimbs. Desmatosuchus is distinct in having large recurved spines on the posterior part of its neck.

D. haplocers skull (from Small 2002) but probably actually D. smalli (Parker)

Ecology

Aetosaurs have long been considered herbivorous, using their skulls and stout forelimbs to dig for soft vegetation and roots, and possibly even insects (Walker 1961). Some parallels can be drawn between aetosaurs and armadillos, due to several convergent characteristics, that may shed light on how aetosaurs fed (Small 2002). Armadillos are considered generalists, but feed predominately on insects and grubs found by digging in the dirt. Such food sources were indeed available for aetosaurs in the Late Triassic. Nests and burrows of various social insects (bees, wasps, termites) have been found in throughout Triassic strata and even fossil wood (Hasiotis, Dubiel, and Demko 1995; Hasiotis and Dubiel 1995). The teeth of Desmatosuchus seem to share characteristics with both herbivorous dinosaurs as well as carnivorous archosaurs (Small 2002). In fact, there may have even been a carnivorous aetosaur living in the Triassic (Murry and Long 1996). All these factors support the possibility of insectivory and/or omnivory among at least some aetosaurs, including Desmatosuchus.

(Personally, I really like the aetosaur/armadillo comparison. And I mean, they even live in the same place! Coincident? I think not!)

Termite burrows (circled in blue) in a siltstone from the Newark Supergroup of Maryland. Picture by Susan Drymala.

The geology of the formations in which Desmatosuchus is found suggests that this animal spent at least some of its time in the floodplains of rivers in ancient Texas, New Mexico, and Arizona (Small 2002; Parker 2008). The rich soils would have supported the insects that have been suggested as the mainstay of the aetosaur diet (Small 2002). Other local inhabitants would have included rauisuchians like Postosuchus and Chatterjeea, other aetosaurs like Paratypothorax and Typothorax, small metaposaurids and other temnospondyls, Arribasuchus and Leptosuchus (phytosaurs), Technosaurus (a dinosaur), and several other taxa including Shuvosaurus and Protoavis (Small 2002; Parker 2008).

Desmatosuchus encounters Postosuchus. Artwork by Douglas Henderson in Dawn of the Dinosaurs: Life in the Triassic by Nicholas Fraser (Plate 7.5A)

Taxonomy
The first material of what we now call Desmatosuchus was described by Cope in 1892 and named Episcoposaurus haplocerus. In 1920, Case first described Desmatosuchus spurensis, which, like E. haplocerus, was considered a phytosaur at the time. Gregory (1953) later revised the taxonomy of Cope and Case, giving us D. spurensis and D. haplocerus as the soul species of Desmatosuchus.

During the last decade or so, there has been a lot of work done on the systematic paleontology of Desmatosuchus. In 2005, Bill Parker erected a new species to the genus, D. smalli. Parker also demonstrated that “D.” chamaensis (Zeigler et al 2002) is more closely related to Paratypothorax than to Desmatosuchus, representing a different genus (2008). Heckert and Lucas (1999) have suggested that Acaenasuchus geoffreyi Long and Murry is a juvenile Desmatosuchus, but Parker cast doubt on this, citing our poor understanding of aetosaur ontogeny and insufficient morphological characters used to refer Acaenasuchus to Desmatosuchus. Finally, because D. haplocerus was found to be nondiagnostic at the species level, we are left with only two valid species: D. spuensis and D. smalli (Parker 2008).

In Popular Culture:

Desmatosuchus has been featured on several TV programs, including Animal Armageddon: Target - Earth and When Dinosaurs Roamed America. There is even a toy Desmatosuchus floating around out there.

In loving memory of Steve Yang.

Feb. 11, 1985 - April 21, 2010