Tapirus terrestris (Linnaeus, 1758)

Holanda, Elizete C. & Rincón, Ascanio D., 2012, Tapirs from the Pleistocene of Venezuela, Acta Palaeontologica Polonica 57 (3), pp. 463-472 : 467-469

Tapirus terrestris (Linnaeus, 1758)

Figs. 3 , 4 .

Material.— Incomplete skull, IVIC−P−2080; incomplete left dentary, IVIC−P−2081; incomplete thoracic vertebrae, IVIC− P−2082, IVIC−P−2083; incomplete left radius, IVIC−P−2077; left humerus, IVIC−P−2088; incomplete left femur, IVIC−P−2076, IVIC−P−2079, IVIC−P−2087; right astragalus, IVIC−P−2084; incomplete right pelvis, IVIC−P−2086; Zumbador Cave , Cerro Misión, Falcón State ( Fig. 1 ), Pleistocene .

Description.—Skull: IVIC−P−2080 is a subadult, with unfused sutures ( Fig. 3A 1 , A 3 ). Only the posterior portions of the parietals are preserved, and form a narrow and high sagittal crest. The occipital is marked by strongly developed and posterolaterally projecting lambdoidal crests. The interparietal region is partially fused. A partial left post−tympanic process and the dorsal margin of external acoustic meatus are all that is preserved of the temporal.

Mandible: IVIC−P−2081 is a left dentary of a young adult bearing p4–m2 and an unerupted m3 ( Fig. 3B ), while missing the coronoid process and the symphyseal region. The body of the dentary is robust and thick. The m1 is slightly worn and marked by perpendicularly arranged lophids, with the protolophid being as wide as the hypolophid. Accessory cuspids and metastylids are absent. The m2 shows little wear and is distinguished by a protolophid exceeding the hypolophid in width.

Postcrania: IVIC−P−2083 is a fractured thoracic vertebra, with a tall and posteriorly inclined spinous process ( Fig. 4A ). The transverse processes are anteroposteriorly elongated, while the mammillary processes are elongate and directed dorsally. IVIC−P−2088 represents an almost complete left humerus ( Fig. 4B ). The proximal part of the head is flatter and wider than its distal part, strongly convex, and sloping distally. The greater tubercle is smoothly curved proximally, greatly increases in thickness anteroposteriorly, and extends to a position above the head of the

http://dx.doi.org/10. 4202/app.2011.0001

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Tapirus terrestris Tapirus webbi Tapirus johnsoni Tapirus mesopotamicus OR1367

Tapirus veroensis Tapirus haysii Tapirus tarijensis Tapirus cristatellus humerus. The deltopectoral crest of the humerus begins at the greater tubercle and extends distally to the deltoid tuberosity, with the latter being very prominent and somewhat rounded. The distal end of the humerus is slightly rounded. IVIC−P−2077 ( Fig. 4C ) represents the proximal end of a left radius, lacking any sign of fusion to the ulna. The radial head is rectangular and wide. The radial tuberosity is developed as a small rugosity.

IVIC−P−2086 corresponds to the iliac part of a right pelvis, in addition to a complete acetabulum ( Fig. 4D ). The latter is about 50 mm in diameter and marked by a distinct fossa extending to its ventral margin, with the latter most likely representing a site of attachment for ligaments. Three fragments of the left femur are preserved. The proximal end (IVIC−P−2076) is transversely wider than it is thick anteroposteriorly. The greater trochanter is broken ( Fig. 4E ), as are

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Tapirus terrestris Tapirus webbi

Tapirus veroensis IVIC-P-2088

the distal portions of the lesser and third trochanters. The body of the femur (IVIC−P−2079) is rather cylindrical in cross section, becoming wider and somewhat flattened distally. The distal end of the humerus (IVIC−P−2087) is transversely wider than it is thick anteroposteriorly, and slightly triangular in shape. The supracondylar fossa is very deep and rough, and lanceolate in outline. IVIC−P−2084 is a heavily eroded right astragalus ( Fig. 4F ). It is slightly square in outline, with the proximal trochlea being inclined at an angle of about 15 degrees with respect to the body. The lateral condyle is higher and projects more proximally than the medial one, and ends abruptly without reaching the plantar surface. The distal articular surface is slightly rectangular and consists of two asymmetrical facets: the navicular facet is rectangular, transversely wider, and thicker dorsoplantarly; by contrast, the cuboid facet is about half the width of the navicular facet, slightly squared, and convex.

Measurements.—IVIC−P−2088: L = 263; MDP = 76.3; CDP = 77; MDH = 55.6; MDB = 29; MDD = 73.4; CDD = 64.4; DTt = 41.1. IVIC−P−2077: MDP = 50; CDD = 26.8.

Remarks.—The cranial anatomy of IVIC−P−2080 resembles that of T. terrestris . Despite being a juvenile, as indicated by the unfused sutures, the specimen displays a fully formed, high and narrow sagittal crest ( Fig. 3A 2 ). By contrast, T. bairdii has a sagittal table and never forms a true sagittal crest (e.g., MLP 1451), while in T. veroensis (UF/FGS277), T. haysii (UF80466), and T. pinchaque (Holbrook 2002) the sagittal crest is low. The crest of the South American fossil tapirs T. mesopotamicus , T. cristatellus , and T. rondoniensis is intermediate in size, being much higher than in T. pinchaque , but lower than that of T. terrestris .

Unlike in any of the North American species, the lambdoidal crests of IVIC−P−2080 are strongly developed and project posterolaterally as in T. terrestris ( Fig. 3B, C ).

The postcranial morphology of Tapirus is rather conservative, and hence of little diagnostic value (Simpson 1945). Wherever possible, the present specimens were compared to other species with preserved postcrania, but, apart from their size, there were few differences. The humerus from Zumbador Cave (IVIC−PV−2088) and that of T. terrestris are virtually identical, and differ from T. webbi and T. veroensis in a more cranially directed greater tubercle. In addition, the supracondylar crest of T. webbi (e.g., UF26225) is very prominent and directed more laterally than in other species. At the present time, we are unable to establish whether these characters can truly distinguish different species, or test their intra− and interspecific variability.

Geographic and stratigraphic range.—South America, Oligocene–Recent.

Figures

Fig. 3. Tapirus terrestris (Linnaeus, 1758), Zumbador Cave, Pleistocene. A. IVIC−P−2080, incomplete skull in lateral (A1), posterior (A2), and dorsal (A3) views. B. IVIC−P−2081, left dentary in lingual view; a, height of the sagittal crest.

Fig. 4. Tapirus terrestris (Linnaeus, 1758), Zumbador Cave, Pleistocene. A. IVIC−P−2083, thoracic vertebra in right lateral view. B. IVIC−P−2088, left humerus in posterior view. C. IVIC−P2077, left radius in anterior view. D. IVIC−P−2086, incomplete right pelvis in lateral view. E. IVIC−P−2076, left femur in anterior view. F. IVIC−P−2084, right astragalus in dorsal view. Scale bars 30 mm.

Fig. 1. Map of the localities in Venezuela from which fossil tapirs have been reported.

Fig. 2. Tapirus sp., El Breal de Orocual, Plio−Pleistocene. A. ORI369, right maxilla in lateral (A1) and occlusal (A2) views. B. ORI367, mandible in labial (B1) and occlusal (B2) views. Scale bars 30 mm.