X-ray computed tomography of two mammoth calf mummies

Abstract

Two female woolly mammoth neonates from permafrost in the Siberian Arctic are the most complete mammoth specimens known. Lyuba, found on the Yamal Peninsula, and Khroma, from northernmost Yakutia, died at ages of approximately one and two months, respectively. Both specimens were CT-scanned, yielding detailed information on the stage of development of their dentition and skeleton and insight into conditions associated with death. Both mammoths died after aspirating mud. Khroma's body was frozen soon after death, leaving her tissues in excellent condition, whereas Lyuba's body underwent postmortem changes that resulted in authigenic formation of nodules of the mineral vivianite associated with her cranium and within diaphyses of long bones. CT data provide the only comprehensive approach to mapping vivianite distribution. Three-dimensional modeling and measurement of segmented long bones permits comparison between these individuals and with previously recovered specimens. CT scans of long bones and foot bones show developmental features such as density gradients that reveal ossification centers. The braincase of Khroma was segmented to show the approximate morphology of the brain; its volume is slightly less (∼2,300 cm3) than that of neonate elephants (∼2,500 cm3). Lyuba's premaxillae are more gracile than those of Khroma, possibly a result of temporal and/or geographic variation but probably also reflective of their age difference. Segmentation of CT data and 3-D modeling software were used to produce models of teeth that were too complex for traditional molding and casting techniques.

A new method of estimating brain mass through cranial capacity in extinct proboscideans to account for the non-neural tissues surrounding their brain

“…2). This morphology exactly mirrors the juvenile morphology of the endocast in young elephants (Shoshani et al, 2006), in the young mammoth Khroma (Fisher et al, 2014), and in its supposed ancestor P. antiquus (Accordi and Palombo, 1971;Palombo, 2001;Palombo and Giovinazzo, 2005). These last authors also showed that the endocranial cavity grew following an intraspecific allometric scaling, resulting in a large endocranial volume with respect to body mass.…”

“…Methods used by previous authors to estimate CC are detailed in the caption of Table 2. Notably, before this study, no estimation of CC has ever been made for an adult Mammuthus primigenius (the CC of the frozen mammoth calf Khroma approximates 2300 cm 3 ; Fisher et al, 2014). Therefore, the double graphic integration method of Jerison (1973) was used to estimate CC from figures of the endocast in dorsal and lateral views, including olfactory bulbs, in Simionescu and Morosan (1937).…”

“…Given that more than 175 fossil species of proboscideans are known (Shoshani and Tassy, 2005), paleoneurological study of those extinct species could compensate for this unfortunate lack of extant diversity. For example, for more than 150 years, biologists and paleobiologists have investigated the cranial cavity of frozen Mammuthus primigenius from Siberia to study the brain of this extinct species (Gleboff, 1846;Salensky, 1904;Kreps et al, 1979Kreps et al, , 1981Maschenko et al, 2013;Fisher et al, 2014), but tissues and structure have always been badly damaged because of ice, mummification, and/or decay.…”

Digitizing, modelling and 3D printing of skeletal digital models of Palaeoloxodon tiliensis (Tilos, Dodecanese, Greece)

“…Recent examples of the use of virtual palaeontology techniques in the study of proboscideans investigate a variety of issues ranging from osteology (Fisher et al, 2014a) to ontogeny and taphonomy (Fisher et al, 2014b), and even dentin density changes in annual increments (Cherney et al, 2014;El Adli et al, 2014) with the use of X-ray tomography.…”

On newborn calf skulls of Early Pleistocene Mammuthus trogontherii from Shanshenmiaozui in Nihewan Basin, China

“…The age determination given by Roth and Shoshani (1988) shows that a three-dayold Asian elephant could have two plates worn on the DP2, but the DP3 was not erupted yet. Among the specimens of M. primigenius, Lyuba's dentition consists of fully formed and almost-erupted deciduous tusks (DI2), fully formed and justerupted DP2s, and incompletely formed and unerupted dP3s and dP4s , Kosintsev et al (2010) refer to her age as "no older than two or three months", and Rountrey et al (2012) and Fisher et al (2014) offered a more precise determination of about one month, based on discovery of a neonatal line in her dentin, marking the time of birth, and postnatal dentin increments in her dP2s.…”