Date of this Version
THE AMERICAN MUSEUM OF NATURAL HISTORY Number 3252, 65 pp.
The oldest known fossil aeluroids are from Lower Oligocene sediments in France (Quercy) and Upper Eocene-Lower Oligocene sediments in Mongolia. These small (< 5 kg) carnivorans are primarily represented by mandibles, with hypercarnivorous dentitions in almost all lineages. The six aeluroid genera from France and those from Mongolia share a common dental pattern despite their geographic separation near the extremes of the Eurasian landmass. This similarity is not surprising, however, because faunal exchange across Eurasia at this time is documented not only by populations of small aeluroids but also by small arctoid carnivorans. Basicrania of Oligocene aeluroids are preserved only in the Quercy deposits. The auditory regions of two genera from Quercy (Palaeoprionodon, Stenoplesictis), and of two additional aeluroid genera (Stenogale, Proailurus) known only from mandibles at Quercy (but matched with congeneric mandibles with associated basicrania from early Miocene sediments at St.-Gerand), reveal a common basicranial morphotype. The living African palm civet Nandinia binotata retains a basicranial and auditory anatomy closely approaching the ancestral aeluroid morphotype. European paleontologists working with the Quercy faunas have regarded several of these aeluroids as early members of the Viverridae and Felidae. However, basicrania of the Quercy and St.-Gerand aeluroids share a common petrosal morphology overprinted by anatomically distinctive and evolutionarily divergent auditory bulla types that differ from those of living felids and viverrids. These basicranial patterns suggest their recent common ancestry more strongly than they support any potential affinity with living viverrids and felids. Among the Quercy crania, only Palaeoprionodon shares significant similarities with a living viverrid, the Asian linsang Prionodon. No early felid crania are known from Quercy deposits. The oldest known basicrania with derived features indicative of felid affinity are those of Proailurus lemanensis and Stenogale julieni, from St.-Gerand, France. They share a derived petrosal morphology that incorporates a uniquely configured bony flange on the medial border of the promontorium. Proailurus lemanensis, long considered to be an ancestral felid, has a particularly distinctive, dorsally depressed petrosal flange produced by auditory bulla hypertrophy. This Proailurus pattern may be derived from the more plesiomorphic basicranium of Stenogale julieni, and together the two genera could be included in a felid subfamily Proailurinae, or, alternatively, the proailurines could be limited to Proailurus and its descendant taxa. Living felids share a morphologically uniform petrosal morphology that lacks the medial flange of the promontorium present in Proailurus and Stenogale. In the living felids the flange is either suppressed and/or reoriented so that it bears no resemblance to the archaic petrosal type. However, the oldest known early and mid-Miocene New World felids (Ginn Quarry, Echo Quarry) described in this study retain archaic petrosals more similar to the petrosal of Proailurus than those of living felids. The origin of the derived petrosal of living felids has yet to be identified among the fossil felids of the later Neogene. The auditory region of the oldest known New World felid (latest early Miocene) from Ginn Quarry, Nebraska, retains a more plesiomorphic petrosal than known in St.-Gerand Proailurus, yet the Ginn Quarry cat is geologically younger. The existence of these two archaic petrosal morphs in early Miocene felids suggests that at least one other felid lineage was present in the early Miocene in addition to Proailurus lemanensis. The subfamily Stenoplesictinae (including Stenoplesictis and Palaeoprionodon) is a paraphyletic taxon lacking reliable derived traits to unite its genera, and the name is no longer employed. The origins of the Herpestidae and Hyaenidae are not illuminated in any way by fossils from Quercy or from Mongolia, and the oldest members of these families are not recorded in the O1- igocene.