Anasinopa leakeyi Savage, 1965

Borths, Matthew R. & Stevens, Nancy J., 2017, Deciduous dentition and dental eruption of Hyainailouroidea (Hyaenodonta, “ Creodonta, ” Placentalia, Mammalia), Palaeontologia Electronica 20 (3), pp. 1-34 : 9-12

Anasinopa leakeyi Savage, 1965

Figures 4-5 , Tables 1-2

Referred specimens. KNM-RU 2385, left maxilla fragment with dP 2, dP 3, and dP 4 (Rusinga Island, Kenya).

Description

The description of the maxillary dentition of Anasinopa leakeyi (KNM-RU 2385, Figure 4 ) is based on a cast deposited in the Rusinga collection at the National Museums of Kenya. A note on the specimen label speculates the original may have been lent to Savage, but the exact location of the original specimen is unknown. The specimen preserves dP 2, dP 3, and dP 4. There is an indentation on the buccal surface of the cast superior to the mesial root of dP 3 that suggests the infraorbital foramen is preserved in the original, though it is not as clear on the cast. The morphology of the dental crowns appears to be accurately captured, with no evidence of bubbles in the plaster, making the detailed description of the deciduous upper dentition possible based on the cast of KNM-RU 2385.

The dP 2 is a buccolingually compressed tooth with a long, low paracone with a height less than half the mesiodistal length of the tooth. A small metastyle is present at the distal point of the tooth, forming a distinct, but small notch between the paracone and metastyle. A clear buccal cingulum traces the buccal surface of the tooth from the

BORTHS & STEVENS: DECIDUOUS HYAENODONT TEETH parastyle to the metastyle. The mesiodistal length of the dP 2 metastyle is less than 25% of the total length of the tooth. The buccal surface of the metastyle is braced by the parastyle of dP 3 such that the buccal face of the dP 2 metastyle is blocked by the parastyle of dP 3 in buccal view.

The dP 3 bears a mesiodistally elongate parastyle that is the same length as the metastyle. The parastyle is a single, distinct cusp that forms a notch where it intersects the preparacrista. The preparacrista rises to the apex of the paracone at a 45 degree angle. The paracone is the tallest cusp on dP 3. The postparacrista is buccolingually compressed, as is the metacone which is a long, low cusp that forms a notch with the postparacrista. The metacone is less than half the height of the paracone. The metastyle forms a distinct carnassial notch with the metacone and rises to the same height as the parastyle and is only half the height of the metacone. On the distobuccal surface of dP 3 is a shallow buccal basin framed by the metacone, metastyle, and buccal cingulum. The protocone projects distolingually from the base of the paracone. The protocone is the same height as the carnassial notch of dP 3. In occlusal view the protocone is triangular, with the mesial and distal margins of the cusp intersecting at a wide angle with no indication of a metaconule or paraconule. A thin lingual cingulum connects the parastyle to the protocone. The metastyle of dP 3 contacts the mesialmost point of the parastyle of dP 4.

The mesiodistal length of dP 4 is only slightly longer than dP 3. The parastyle of dP 4 is smaller and more cingulum-like than the distinct, cusp-like parastyle on dP 3. On dP 4 a distinct buccal cingulum connects the parastyle to the metastyle. Distal to the parastyle, the paracone and metacone are divergent cusps from their bases to their apices. The paracone is only slightly buccolingually compressed, and its base is circular in cross section. The metacone is more buccolingually compressed than the paracone and is more lingually positioned than the paracone. The postmetacrista is sectorial, forming a deep carnassial notch with the metastyle. The mesiodistal length of the metastyle is subequal to the mesiodistal length of the metacone base. The metastyle is blade-like with a distinct convex crista that gently inflects distally. The metastyle does not connect to the protocone. Instead, a large metaconule that is the same height as the carnassial notch arises near the distal base of the metacone. A small, but distinct notch is formed between the metaconule and protocone. The protocone is a tall cusp that is subequal in height to the paracone. The apex of the protocone points in a mesiobuccal direction. Compared with the protocone of dP 3, the protocone of dP 4 is mesially shifted and buccolingually aligned with the paracone in occlusal view. The mesial margin of the protocone forms a small notch with the paraconule. The paraconule is as large and welldefined as the metaconule. A thin lingual cingulum connects the paraconule to the parastyle. The large protocone, paraconule, metaconule, and divergent paracone and metacone frame a wide and deep trigon basin. The mesial roots of M 1 are preserved on the specimen, indicating the protocone of M 1 projected more lingually than the protocone of dP 4. The mesiobuccal root of M 1 also indicates the metastyle of dP 4 was aligned with the parastyle of M 1.

Morales et al. (2010) described portions of the lower deciduous dentition of Anasinopa libyca from the early middle Miocene of Libya. Here we provide additional description of this specimen ( Figure 5 ), discovered by R. J. G. Savage, which preserves the morphology dP 3 and dP 4. There is a short diastema between the distal alveolus of dP 2 and dP 3. dP 3 is buccolingually compressed with a mesiodistally extensive paraconid. dP 3 is heavily abraded, but there was a distinct talonid basin. Like dP 3, the trigonid of dP 4 is buccolingually compressed. The bases of the paraconid and protoconid are subequal in length. The postprotocristid slopes to a small metaconid at the distal-most margin of the protoconid base. The small metaconid is less than half the height of the protoconid. The talonid basin of dP 4 is shallow, and enclosed lingually by the entocristid, which connects with the base of the metaconid. The talonid basin of dP 4 is demarcated by a low, but distinct hypoconid and hypoconulid and a slight entoconid that grades into the entocristid.

Remarks

Recent phylogenetic analyses resolve Anasinopa within Teratodontinae , an entirely Afro-Arabian clade ( Solé et al., 2014; Rana et al., 2015; Borths and Seiffert, 2017). In the topologies described by Borths et al. (2016) and Borths and Seiffert (2017) Teratodontinae is the sister clade of Hyainailouridae ( Apterodontinae + Hyainailourinae ). Teratodontinae is generally characterized by dental features shared with mesocarnivores including divergent paracones and metacones, basined talonids, and the presence of metaconids. However, within Teratodontinae , some taxa, like Anasinopa , combine this mesocarnivorous morphology with hallmarks of hypercarnivores like exaggerated metastyles and tall, buccolingually compressed metacones. Borths et al. (2016) demonstrated that teratodontines specifically converged with the hypercarnivorous dental morphology of Hyaenodontinae. Despite convergent features associated with hypercarnivory, synapomorphies between the deciduous dentition of Anasinopa and the deciduous dentition of other teratodontines consistently place this hypercarnivorous, wolf-sized hyaenodont within Teratodontinae .

In several recent phylogenetic analyses ( Rana et al., 2015; Borths and Seiffert, 2017) Dissopsalis and Anasinopa are closely related taxa within Teratodontinae and both taxa are found in early to middle Miocene sites. The two genera differ in size, with Anasinopa slightly smaller than Dissopsalis . The adult dentitions of Dissopsalis and Anasinopa both mix mesocarnivorous and hypercarnivorous dental features, with M 1 and M 2 retaining the well-developed talonid basins of mesocarnivores, but the talonid of M 3 reduced to a single cusp and the carnassial blade of M 3 expanded as would be expected in hypercarnivores. When Dissopsalis and Anasinopa are directly compared, Dissopsalis has more exaggerated hypercarnivorous dental features, with more reduced paracones on the upper molars and more elongate carnassial blades.

The maxillary specimen, KNM-RU 2385 ( Figure 4 ), is consistent in size with Anasinopa and the expanded trigon basins, mesiodistally shorter metastyles, and widely divergent paracone and metacone on dP 4 are also consistent with the adult dental morphology of Anasinopa . The deciduous dentition of Anasinopa and Dissopsalis are similar, although several characters can be used to distinguish these taxa. Anasinopa has a dP 3 metacone that is mesiodistally shorter than the dP 3 metacone of Dissopsalis . Further, the metastyle on dP 3 in Anasinopa is also mesiodistally shorter than the dP 3 metastyle of Dissopsalis . The dP 3 buccal cingulum of Anasinopa is wider and more distinct than is the buccal cingulum of Dissopsalis . Like the metastyle on dP 3, the metastyle of dP 4 in Anasinopa is relatively shorter than the metastyle on dP 4 in Dissopsalis . The protocone on dP 4 of Anasinopa bears a more distinct paraconule and metaconule than the protocone of dP 4 in Dissopsalis , and the margins of the protocone in Anasinopa meet at a wider angle, giving the protocone a broader, triangular shape in occlusal view than the mesiodistally narrowed dP 4 protocone of Dissopsalis .

Masrasector is also nested within Teratodontinae and is closely related to Anasinopa . Anasinopa is larger than Masrasector , but the two taxa share divergent metacones and paracones on dP 4. Also on dP 4 in both Masrasector and Anasinopa , the metacone is lingually placed relative to the paracone rather than mesiodistally aligned with the paracone as it is in Dissopsalis , Leakitherium , and Apterodon . The divergent dP 4 paracones, metacones, and protocones of both Masrasector and Anasinopa surround broad trigon basins.

In teratodontines the M 1 and M 2 paracones are subequal to or lower than the metacones, leaving the metacone as the lead piercing cusp on the molars. In Anasinopa , dP 4 anticipates the morphology of the adult molars by exhibiting a slightly taller metacone than paracone, morphology that is shared with the dP 4 of Masrasector . The dP 4 of Anasinopa shares with the dP 4 of the teratodontines Brychotherium , Masrasector , and Metasinopa , a broad shelf between the metastyle, metacone, and buccal cingulum. Dissopsalis lacks this broad distal buccal shelf.

The dentary of Anasinopa libyca preserves dP 3 and dP 4 ( Figure 5 ). Morales et al. (2010) noted A. libyca is 10 to 25% smaller than A. leakeyi , the species to which we refer KNM-FT 3357. dP 4 in A. libyca shares with the dP 4 of Masrasector and Metasinopa a distinct metaconid that is only slightly lower than the paraconid. These three teratodontines also share a mesiodistally elongate talonid basin with distinct hypoconids and hypoconulids. A. libyca and Metasinopa differ from Masrasector in lacking distinct entoconids on the lingual margin of the talonid basin. Instead, A. libyca and Metasinopa both exhibit smooth entocristids that close the lingual margin of the talonid.

Figures

FIGURE 4. Anasinopa leakeyi left maxilla cast with dP2, dP3 and dP4 (KNM-RU 2385) from Rusinga Island (early Miocene), Kenya in 1) occlusal view; 2) buccal view; and 3) lingual view. Scale bar is 10 mm.

FIGURE 5. Anasinopa libyca left dentary with dP3 and dP4 from Gebel Zelten (middle Miocene), Libya (BMNH M82378) in 1) occlusal view; 2) lingual view; 3) buccal view. Scale bar is 10 mm.