The earliest ossicone and post-cranial record of Giraffa
September
The earliest ossicone and post-cranial record of Giraffa
Melinda Danowitz 0 1
John C. Barry 1
Nikos Solounias 0 1
0 Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine , Old Westbury, NY , United States of America, 2 Department of Pediatrics, A.I. DuPont Hospital for Children, Wilmington, DE, United States of America, 3 Department of Human Evolutionary Biology, Peabody Museum , Harvard, Cambridge, MA , United States of America, 4 Department of Paleontology, American Museum of Natural History , New York, NY , United States of America
1 Editor: James J. Cray, Jr., Medical University of South Carolina , UNITED STATES
The oldest Giraffa material presently known consists of dental specimens. The oldest postcranial Giraffa material belongs to the Plio-Pleistocene taxon Giraffa sivalensis, where the holotype is a third cervical vertebra. We describe three non-dental specimens from the Early Late Miocene of the Potwar Plateau, including an 8.1 million year old ossicone, 9.4 million year old astragalus, and 8.9 million year old metatarsal and refer them to Giraffa. The described ossicone exhibits remarkable similarities with the ossicones of a juvenile modern giraffe, including the distribution of secondary bone growth, posterior curvature, and concave pitted undersurface where the ossicone would attach to the skull. The astragalus has a notably flat grove of the trochlea, medial twisting between the trochlea and the head, and a square-shaped sustentacular facet, all of which characterize the astragalus of Giraffa camelopardalis. The newly described astragalus is narrow and rectangular, unlike the boxy shaped bone of the modern giraffe. The metatarsal is large in size and has a shallow central trough created by thin medial and lateral ridges, a feature unique to Giraffa and Sivatherium. Our described material introduce the earliest non-dental material of Giraffa, a genus whose extinct representation is otherwise dominated by teeth, and demonstrate that the genus has been morphologically consistent over 9 million years.
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Data Availability Statement: All relevant data are
within the paper.
Funding: The authors received no specific funding
for this work.
Competing interests: The authors have declared
that no competing interests exist.
Introduction
Giraffa is currently represented by four extant species that are found throughout Africa [
1
].
These distinct species have been separated using differences in the nucelear and mitochondrial
genetic makeup, however the skeletal and soft anatomy of the four taxa has yet to be studied
and described. The oldest representatives of this genus include Giraffa priscilla and Giraffa
punjabiensis, taxa that are known from the Middle and Lower Siwaliks [2±4]. Giraffa priscilla
and Giraffa punjabiensis have been named based on teeth, and subsequent studies have
referred additional dental specimens to these taxa [5±11]. Younger Giraffa species are known
from the Pliocene and the Plio-Pleistocene, including Giraffa sivalensis from the Upper
Siwaliks [
2,12
], and Giraffa jumae and Giraffa stillei from localities in East Africa [13]. Our study
introduces for the first time post-cranial material of Giraffa from the Middle Siwaliks,
providing the oldest known non-dental specimens of this genus.
While there are currently only two extant genera of Giraffidae, the okapi (Okapia) and the
giraffe (Giraffa), the Late and Middle Miocene sampled a more diverse array of giraffids
throughout Africa, Europe and Asia. Among these, Samotherium major and Giraffokeryx
punjabiensis are the better known. Although sampled from the Late and Middle Miocene of the
Potwar Plateau, Giraffa punjabiensis and Giraffa priscilla are less well known. Dental material
from Giraffa punjabiensis has been reported along with sivatheres from the Dhok Pathan
Formation [
3
], which ranges from 10.1±3.5 Ma [
14
]. Giraffa priscilla, a slightly older taxon, has
been reported along with the better known giraffid Giraffokeryx punjabiensis from the Chinji
Formation [
2
], which ranges from 14±10.8 Ma [
15
].
Giraffa sivalensis is a geologically younger species of Giraffa known from the Upper Siwaliks
[
2
]. This was the first extinct Giraffa species found, and unlike Giraffa priscilla and Giraffa
punjabiensis where the type specimens are dentitions, the holotype of Giraffa sivalensis is a third
cervical vertebra [
12
]. Giraffa sivalensis is based on both dental and post-cranial material; the
skeletal specimens allow for hypotheses regarding neck elongation and general body and
metapodial size. Features of the third cervical vertebra support the theory that Giraffa sivalensis is
transitional in the elongation of the posterior portion of the vertebra, the stage responsible for
the extreme elongation that characterizes the neck of the modern giraffe [
16
]. Body size
analyses incorporating the neck, teeth, and limbs also allow for the evaluation of potential se (...truncated)