Prolacerta broomi (Parrington 1935, Early Triassic, ~250 mya, BPI 2675) was originally considered ancestral to lizards, especially the long-necked Macrocemus and Tanystropheus, but it is not related according to the present reptile tree. Rather, this genus is at the base of the protorosaurs and at the base of lineage that led ultimately to dinosaurs, birds and all the Archosauriformes. Prolacerta was derived from a sister to Protorosaurus. Prolacerta phylogenetically preceded the Boreopricea clade and the Jaxtasuchus clade.

The skull of Prolacerta had a longer, straighter rostrum and the quadratojugal was reduced to a sliver on the quadrate. The postorbital was more robust. The nares opened dorsolaterally. The quadrate leaned anteriorly. The orbit and lateral temporal fenestra were relatively smaller. The teeth were longer. The cervicals were all elongated. The tail tapered to a slender whip. The chevrons were deeper anteriorly, but shallower posteriorly. The pectoral girdle was taller, extending to the top of the vertebrae, and more robust. Manual digits 1 and 5 became reduced and the entire manus was relatively smaller. The ilium was elongated dorsally. The pedal digits were relatively shorter as the metatarsals were longer. Metatarsal 5 was shorter with an "L"- or hook-shape.

Ozmik volans (Dzik and Sulej 2016; Late Triassic) was originally described as a larger sister to Sharovippteryx due to its extraoridnarily long and slender limbs and elongate neck. Here it nests with Prolacerta. The girdles are smaller than in a similar-sized Prolacerta indicating a great reduction in the size of the limb muscles. Was this a floating predator? It does not look able to walk well on such spidery limbs. Perhaps it rode the wide flat skull of the giant amphibian, Metoposaurus (see below).

Prolacerta broomi (originally Pricea longiceps, Broom and Robinson 1948, BPI/1/471) is the best preserved skull. No post-crania is known.

Vellbergia bartholomei (Sobral, Simoes and Schoch 2020; Middle Triassic; 1.5cm skull) was originally described (without a reconstruction) as a hatchling stem lepidosauromorph with long jaws. Here it nests as hatchling Prolacerta close to the BPI/1/471 specimen.

The AMNH 9520 skull of Prolacerta found in Antarctica is basal to all remaining protorosaurs. The short rostrum is retained from ancestral basal younginiforms.

Ixalerpeton polesinensis (Cabreira et al. 2016; Late Triassic, Carnian 230mya) was originally considered a sister to Lagerpeton but here nests with the AMNH 9520 specimen of Prolacerta, with a small scapula, like Malerisaurus and a short cervical series like Boreopricea.

Venetoraptor gassenae (Müller et al 2023, Late Triassic, 1m? length) was originally considered a sister to Lagerpeton, and close to pterosaurs, but here nests within Protorosauria as a likely biped, given the relative leg length and trenchant manual unguals. This would be the first protorosaur biped, not a pterosaur ancestor.

Czatkowiella harae (Borsuk−Biaynicka & Evans 2009) Early Triassic ~250 mya, was recently described as a long-necked sister to Protorosaurus, but if the scale bars are correct, Czatkowiellla had a more gracile neck that was not longer than that of other protorosaurs. Here it nests with long-necked Ozimek (below). Several sizes are known, all from disarticulated bone fragments. The number of cervicals is therefore unknown. Hopefully all of the bones assigned to this genus actually belong to this genus.

Distinct from Protorosaurus, the skull of Czatkowiella was longer, lower, flatter and wider. The maxilla ascended in a process just aft of the long naris. The jugal had a stub quadratojugal process. The descending process of the squamosal was gracile and acute. The upper temporal fenestra was smaller. The lateral processes of the parietal were more posteriorly oriented.

The cervicals and dorsals were shallower with lower neural spines.

The gamut of known protorosaurs, including a sister of their common ancestor, Orovenator. Youngina is a sister to the protorosaurs ancestral to the Archosauriformes. Click to enlarge. Taxa once considered prolacertiforms, such as Tanystropheus and Sharovipteryx, now nest within the Tritosauria within the Squamata.

Borsuk−Biaynicka M and Evans S E 2009. A long−necked archosauromorph from the Early Triassic of Poland. Paleontologica Polonica 65: 203–234.

Cabreira SF et al. (13 authors) 2016. A unique Late Triassic dinosauromorph assemblage reveals dinosaur ancestral anatomy and diet. Current Biology (2016), http://dx.doi.org/10.1016/j.cub.2016.09.040

Dzik J and Sulej T 2016. An early Late Triassic long-necked reptile with a bony pectoral shield and gracile appendages. Acta Palaeontologica Polonica 61 (4): 805–823.

Gow CE 1975. The morphology and relationships of Youngina capensis Broom and Prolacerta broomi Parrington. Palaeontologia Africana, 18:89-131.

Modesto SP and Sues H-D 2002. The skull of the Early Triassic archosauromorph reptile Prolacerta broomi and its phylogenetic significance. Zoological Journal of the Linnean Society, 140:335-351.

Müller RT et al (8 co-authors) 2023. New reptile shows dinosaurs and pterosaurs evolved among diverse precursors. Nature. 620 (7974): 589–594.

Parrington FR 1935. On Prolacerta broomi gen. et sp. nov. and the origin of lizards. Annals and Magazine of Natural History 16, 197–205.

Sobral G, Simoes TR and Schoch RR 2020. A tiny new Middle Triassic stem-lepidosauromorph from Germany: implications fro the early evolution of lepidosauromorphs and the Vellberg fauna. Nature.com Scientific Reports 10, Article number: 2273.

Spiekman SNF 2018. A new specimen of Prolacerta broomi from the lower Fremouw Formation (Early Triassic) of Antarctica, its biogeographical implications and a taxonomic revision. Nature.com/scientificreports 8:17996

wiki/Prolacertiformes
wiki/Protorosauria
wiki/Venetoraptor
wiki/Prolacerta
wiki/Czatkowiella
wiki/Ozimek_volans
wiki/Ixalerpeton