A New Species of Garjainia Ochev, 1958 (Diapsida: Archosauriformes: Erythrosuchidae) from the Early Triassic of South Africa

Abstract

A new species of the erythrosuchid archosauriform reptile Garjainia Ochev, 1958 is described on the basis of disarticulated but abundant and well-preserved cranial and postcranial material from the late Early Triassic (late Olenekian) Subzone A of the Cynognathus Assemblage Zone of the Burgersdorp Formation (Beaufort Group) of the Karoo Basin of South Africa. The new species, G. madiba, differs from its unique congener, G. prima from the late Olenekian of European Russia, most notably in having large bony bosses on the lateral surfaces of the jugals and postorbitals. The new species also has more teeth and a proportionately longer postacetabular process of the ilium than G. prima. Analysis of G. madiba bone histology reveals thick compact cortices comprised of highly vascularized, rapidly forming fibro-lamellar bone tissue, similar to Erythrosuchus africanus from Subzone B of the Cynognathus Assemblage Zone. The most notable differences between the two taxa are the predominance of a radiating vascular network and presence of annuli in the limb bones of G. madiba. These features indicate rapid growth rates, consistent with data for many other Triassic archosauriforms, but also a high degree of developmental plasticity as growth remained flexible. The diagnoses of Garjainia and of Erythrosuchidae are addressed and revised. Garjainia madiba is the geologically oldest erythrosuchid known from the Southern Hemisphere, and demonstrates that erythrosuchids achieved a cosmopolitan biogeographical distribution by the end of the Early Triassic, within five million years of the end-Permian mass extinction event. It provides new insights into the diversity of the Subzone A vertebrate assemblage, which partially fills a major gap between classic ‘faunal’ assemblages from the older Lystrosaurus Assemblage Zone (earliest Triassic) and the younger Subzone B of the Cynognathus Assemblage Zone (early Middle Triassic).

Cranial Anatomy and Palaeoneurology of the Archosaur Riojasuchus tenuisceps from the Los Colorados Formation, La Rioja, Argentina

“…The jugal of Riojasuchus tenuisceps (PVL 3827, 3828) has an anteroposteriorly short lateral protuberance on the ventral margin of its central region ( Fig 2B :J.pb). It differs from the ridge seen on the lateral surface of the jugal of Ornithosuchus longidens (NHMUK PV R 3142) but slightly resembles the protuberance seen in Garjainia madiba [ 29 ], although it is not so expanded laterally.…”

Post‐hatchling cranial ontogeny in the Early Triassic diapsid reptile Proterosuchus fergusi

“…, ; Sookias & Butler, ; Gower et al. ). By contrast, other Triassic basal archosauromorphs known from extensive and ontogenetically variable samples possess highly specialised skulls, and their ontogenetic trajectories are probably not useful models for understanding broader macroevolutionary processes (e.g.…”

Osteohistology of the silesaurid Sacisaurus agudoensis from southern Brazil (Late Triassic) and implications for growth in early dinosaurs

“…An unidentified long bone of the proterochampsid Chanaresuchus bonapartei romer 1971 reveals similar bone tissues, but with a more sub-reticular vascular arrangement in the inner cortex (ricqlès et al 2008). Several elements from different individuals of the large-bodied triassic erythrosuchids Erythrosuchus africanus Broom 1905 (Gross 1934, ricqlès 1976, ricqlès et al 2008, Botha-Brink and Smith 2011 and Garjainia madiba Gower et al 2014(Gower et al 2014) exhibit a variety of vascular arrangements including laminar, reticular and radial, within a fibrolamellar bone complex, indicating rapid growth rates, similar to those found in fast-growing dinosaurs. Although faster growing tissues become more prevalent among non-archosaurian archosauriforms, it should be (Nesbitt et al 2009).…”

“…these taxa show that there was some degree of experimentation amongst the triassic non-archosaurian archosauriforms as shown by the variety of bone tissue patterns in this group. however, the increasing prevalence of highly vascularized fibrolamellar bone shows that rapid growth rates evolved before the origin of Ornithodira (ricqlès et al 2008, Botha-Brink and Smith 2011, Gower et al 2014 and is considered plesiomorphic for archosauriforms (ricqlès et al 2003). the simpler vascular pattern seen in silesaurids differs from most early dinosaurs where the vascular arrangements tend to exhibit more complex anastomosing.…”