Date of this Version
The Prairie Naturalist • 50(2): December 2018
On 6 April 2018 a female white-tailed deer (Odocoileus virginianus dakotensis) was hit and killed by a vehicle along HWY 1806 in rural Morton County, North Dakota, USA (N46o 38.617; W100o 42.901). Based upon dental eruption and wear (Severinghaus 1949), the female was estimated to be a >4.5 years-of-age. A male fetus with parapagus diprosopus (i.e., shared face) apparently was expelled from the adult female, and a domestic canine (Canis lupus familiaris) carried the fetus to a private residence. The resident contacted the North Dakota Game and Fish Department (NDGFD) to turn in the fetus. On 10 April 2018, NDGFD employees attempted to retrieve the carcass of the adult female; however, coyotes (Canis latrans) had scavenged most of the carcass, leaving only the head, spinal column, and legs.
Fetus measurements were as follows: total length (right head), 430 mm; chest girth circumference 245 mm; hindfoot length, 135 mm; left head circumference 200 mm; right head circumference 182 mm; combined head circumference 268 mm; and weight 1520 g. We estimated the fetus to be 136 to 143 days old, based upon hindfoot length and fetus weight, respectively (Short 1970). Duplication of the heads was incomplete, as they were joined laterally at the right mandible of the left head and the zygomatic arch of the right head, with the sagittal crests of the two heads forming an angle of about 60o (Fig. 1). Both heads shared an ear (Fig. 2). Radiography revealed the heads were jointly attached to the spinal column at the first cervical vertebra (Fig. 3). It is doubtful that this fetus could have survived birth, and it is possible it would have resulted in dystocia and death of the dam (D.M. Grove, DVM, personal observation). Diprosopus is a very rare congenital abnormality; in humans (Homo sapiens) conjoined twins occur at a rate of about 4 to 19 per 1,000,000 births, and diprosopus occurring about 2 per 1,000,000 births (Chih-Ping et al. 2011, Bidondo et al. 2016). It has been suggested this malformation, at least on occasion, is the result of a genetically imperfect embryo; that is most commonly accompanied by a non-functional heart or a competent brain (Spencer 2001).