Proailurus: The First Cat

Proailurus, as I mentioned in my first blog, is latin for 'first cat' because it is currently accepted as the first 'true cat' and thus the earliest felid known to modern science. Proailurus was a part of the Proailurinae subfamily which appeared around 35 million years ago and included three known species; P. lemanensis, P. bourbonnensis and P. major. P. lemanensis has the most extensive fossil record and is illustrated below in figure 1. Proailurus was a medium sized cat with similar dimensions to a modern bobcat. Although the dentition of Proailurus does differ to modern cats with slightly different dental topography and the reduction of certain elements, overall dental characteristics show a remarkable resemblance to living felids (Werdelin et. al. 2009). As seen in figure 1, the body structure of Proailurus also exhibits a great likeness to extant cats. The auditory bulla (the structure which houses the middle ear) and postcranium of P. lemanensis are the only other characteristics that appear to be distinctive from other felid subfamilies. So essentially, apart from a few dissimilarities, Proailurus is a modern felid with somewhat shorter limbs (Werdelin et. al. 2009).

Figure 1. An artist's reconstruction of Proailurus lemanensis (Werdelin et. al. 2009).

Fossils of Proailurus have only been discovered in Europe, most fossils of P. lemanensis have been found in France. A study by Hunt (1998) described the basicranial structure of a Proailurus-grade felid from Ginn Quarry in Nebraska suggesting that the phylogenetic diversification of the Felidae family had already begun in the Early Miocene and that felids may have migrated into North America around 19 Ma together with other carnivoran taxa (Werdelin et. al. 2009). From Proailurus the phylogenetic tree would then branch out into two major clades; Machairodontinae and Felinae. The Acinonyx genus is usually included in the Felinae subfamily but in this blog it will be discussed separately. Despite what is now known on the origins of the Felidae family, the path preceding the current felid condition has always been obscure. Hence, there will continue to be some level of uncertainty in cat phylogenetics.

References:

• Hunt, RM 1998, 'Evolution of the aeluroid Carnivora. Diversity of the earliest aeluroids from Eurasia (Quercy, Hsanda-Gol) and the origin of felids', American Museum Novitates, no. 3252.
• Werdelin L, Yamaguchi N, Johnson WE, and O’Brien SJ 2009, 'Phylogeny and evolution of cats (Felidae)', in Macdonald DW & Loveridge AJ (ed.), Biology and Conservation of Wild Felids, Oxford University Press, pp. 59-82.