Broomia – A sister for Milleropsis – not Milleretta

Figure 1. Broomia. A long-recognized sister to Milleropsis, an early possible biped. Check out those thighs!

Figure 1. Broomia. A long-recognized sister to Milleropsis, an early possible biped. Check out those thighs!

Broomia perplexa (Watson 1914, Thommasen and Carroll 1981, Middle Permian) was considered a millerettid and a descendant of romerid – catorhinomorphs, considerably older than other millerettids. The large reptile tree nested Broomia away from the millerettids among the new Lepidosauromorpha, but right next to Milleropsis, among the new Archosauromorpha close to the origin of the Diapsida and Petrolacosaurus. A shame we can’t see the top of the skull! Those long legs, robust femora, strong tarsals and large feet give the impression that Broomia was a strong runner.

Millerettids perplexed Carroll in 1981 and again in 1988 in the days before phylogenetic analysis. Today, due to the large reptile tree, we know the original members are diphyletic (not related), but developed similar traits by convergence.

Broomia has a lateral temporal fenestra derived from basal synapsid ancestors like Aerosaurus and Heleosaurus. mimicking millerettids and caseids. Unlike lepidosaurs, Broomia lacked an ossified sternum or fenestrated pectoral girdles.

Thommasen and Carroll (1981) note the disappearance of the millerettids about the time that lizards first appeared in the Late Permian. Millerettids gave rise to turtles and lepidosaurs via owenettids and early lepidosauriformes. Milleropsids, like Broomia, gave rise to enaliosaurs and protorosaurs, which ultimately produced archosaurs.

References
Thommasen H and Carroll RL 1981. Broomia, the Oldest Known Millerettid Reptile. Paleontology 24(2): 379-390.
Carroll RL 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York 1-698.
Watson  DMS 1914. Broomia perplexa gen et sp. nov., a fossil reptile from South Africa. Proceedings of the Zoological Society of Londont 995-1010.

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