[D] Technosaurus smalli [Su] [sG] [T]
Triassic Late Carnian
Ornithischia? Incertae Sedis
Miller\\\\\\\'s Ranch, near Post, Garza County, Dockum Group, Cooper Canyon Formation, Texas, US
Genus - Typespecies - Skull
Taxonomic placement by Nesbitt, S.J., Irmis, R.B. and Parker, W.G. (2007): Valid taxon of Archosauriformes.
Isolated skull and skeletal elements.
Technosaurus smalli is the earliest adequate record of an ornithischian found to date in Laurasia, and gives an insight about the origin and evolution of this interesting group of dinosaurs. The material is represented by partial jaws with well-preserved teeth, a dorsal vertebra, and an astragalus. The presence of lateral mandibular fenestra and the thecodont type of tooth implantation suggests its archosaurian affinity. The astragalus is of standard dinosaurian pattern with an ascending process for locking the tibia.
The compressed, leaf-like form of its teeth, with denticulated edges, is like that of ornithischians. The teeth are marginally placed, not inset, and continue to the tip of the premaxilla. The teeth are not worn down by tooth-to-tooth contact. The tooth crown is symmetrical with practically no curvature of the dentary tooth laterally. These dental characters are diagnostic of the family [Fabrosauridae].
Technosaurus smalli, however, is sufficiently distinct from known [fabrosaurids] in detailed morphology to warrant a separate generic status. The fragments were found in the red mudstone facies of the fluvial Dockum Group in the summer of 1983, near Post, Garza County, West Texas.
A quarry here has recently produced a variety of rich assemblages of tetrapod remains documenting the following groups: parasuchids, metoposaurs, aetosaurs, poposaurs, ictidosaurs, microsaurs, lizards, pterosaurs, and possible snakes. Such a rich occurrence is very rare in the Dockum. The association of metoposaur and parasuchid clearly indicates the Upper Triassic (Carnian-Norian) age for the Dockum Group.
Derivation of name
The generic name is given in honor of Texas Tech University, the specific name in recognition of the generous help afforded by Bryan J. Small in the field and laboratory.
TTU P 9021. Partial jaws with well-preserved teeth, a vertebra and an astragalus in the collection of the Texas Tech University Museum.
A primitive [fabrosaur], skull twice the size of that of Lesothosaurus and Scutellosaurus. Tooth crown low with flutings at the base; teeth heterodont, marginally placed. Premaxillary teeth conical, cheek teeth closely packed with overlap between the crown of adjacent teeth; 3 cusps in the crown lined antero-posteriorly, connected by sharp, denticulated edges; central cusp main (mcc), anterior (aae) and posterior (pac) cusps accessory; crowns symmetrical in side view and completely enamelled, lacking wear facets; special foramina for replacement teeth absent; coronoid process high; very large external mandibular fenestra.
Dorsal vertebra amphicoelous; transverse process long and compressed; parapophysis widely separated from diapophysis; astragalus elongated medio-laterally with an ascending process for locking the tibia; lateral tibial facet elongated, medial calcaneal facet small and concave; ankle joint Advanced- Mesotarsal (AM) type.
Remarks by Nesbitt, S.J., Irmis, R.B. and Parker, W.G. (2007)
The teeth of Technosaurus are diagnosable and thus, Technosaurus is valid, but because the holotype material consists only of a dentary and premaxilla with ‘thecodont tooth’ implantation, a robust assignment more inclusive than Archosauriformes is not possible.