Microchiroptera, Dobson, 1875

Harrison, David L. & Hooker, Jeremy J., 2010, Late Middle Eocene bats from the Creechbarrow Limestone Formation, Dorset, southern England with description of a new species of Archaeonycteris (Chiroptera: Archaeonycteridae), Acta Chiropterologica 12 (1), pp. 1-18 : 12-15

Microchiroptera gen. et sp. indet.

Material

HZM 22.34774 trigonid right lower molar: TRI W 0.77 ; TRI L 1.66; PH 1.28 ( Figs. 5 E–H, 8G–I).

Description

This is a small gracile right trigonid. It is certainly different from all the Creechbarrow taxa described above. The cusps are completely unworn, so that their relative height is clearly determined. The protoconid is dominant, the metaconid high, attaining three-quarters of its height in distal view; the paraconid is lowest, connected to the protoconid by a shallow concave paracristid. Distally there is a distinct median trigonid notch, with the attachment of

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the cristid obliqua directly below it and at a lower level than the broken off pre-entocristid lingually. The robust buccal cingulum is broken off just distal to the protoconid and extends to a point buccal to the paraconid. There are no crenulations visible on it, but a shallow concavity is present midway along its mesial border.

The trigonid basin is widely open and the lingual aspect of the protoconid has a distinct vertical ridge (bordered on both sides by hairline cracks), and with distinct hollows both mesial and distal to the ridge, which passes to the base of the metaconid.

Discussion

It does not resemble the trigonids of modern emballonurids compared or of Vespertiliavus . It is equally incompatible with Recent small molossids or with Kerivoula hardwickei , all of which have notably lower paraconids as well as other differences.

The closest similarity to a described bat is with Ageina tobieni Russell, Louis and Savage, 1973 from the Early Eocene of Mutigny, France. The right M 1 M. N.H.N – Mu 5112 shares with the Creechbarrow trigonid the presence of a lingual protoconid rib (not shown in their fig. 8f) passing to the

metaconid and it appears compatible in size and general morphology. Intact teeth are needed, since this small species may possibly represent Ageina ; meanwhile its identity is obscure. Ageina remains of uncertain familial affinity.

Figures

FIG. 5. Creechbarrow bats. Stehlinia quercyi HZM 4.36362. Right C1 in A — distal, B — lingual, C — buccal and D — occlusal views. Arrow indicates mesiolingual cusp. Scale = 1 mm. Microchiroptera gen. et sp. indet. HZM 22.34774. Right trigonid of lower molar in E — buccal, F — distal, G — lingual and H — occlusal views. Rhinolophidae gen. et sp. indet. HZM 2.38159. Right

Left M1/2 in G — distal, H — lingual, I — buccal and J — occlusal views. Scale = 1 mm