Aegyptocetus tarfa

The fossil of this early primitive whale was found cut into multiple slabs from a marbleized limestone imported in Italy. Put back together, it reveals an unusual Protocetid whale with a peculiar skull angled more like the Remingtonocetids such as Remingtonocetus and Dalanistes than the other protocetids and the basilosaurids. Bite marks on the ribs indicated that this particular individual was attacked by a large shark. The fossil came from the Gebel Hof Formation (Middle Eocene) of Wadi Tarfa in the Eastern Desert of Egypt.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)

Reference:

G. Bianucci and P. D. Gingerich. 2011. Aegyptocetus tarfa, n. gen. et sp. (Mammalia, Cetacea), from the middle Eocene of Egypt: clinorhynchy, olfaction, and hearing in a protocetid whale. Journal of Vertebrate Paleontology 31(6):1173-1188

Hyracotherium & Mesohippus

Starting a series of illustrations on the Early horses...

The 40 cm tall early horse Hyracotherium (= Eohippus) was widely distributed along the northern hemisphere during the Early Eocene period, 55-45 millions years ago. Several species have been described. This small creature lived in forest environments, probably in herds.

The later Mesohippus was a bit larger, standing at 60 cm in height, with longer legs. The different species were distributed from the Late Eocene to the Middle Oligocene periods (40-30 MYA) throughout the forests of the North American continent.


Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.

Cryptolacerta hassiaca

Fig 1.- Iberian worm lizards (Blanus cinereus)  by Richard Avery, from Wikipedia.

The worm lizards form a peculiar group of burrowing and legless reptiles that have a superficial resemblance to earthworms. These odd critters were traditionally placed in their own suborder, the Amphisbaenians, alongside the other two groups of Squamates, the snakes (Serpentes) and the lizards (Lacertilia). Molecular data (Townsend et al., 2004; Vidal et al., 2005) however have shown that they are in fact closely related to a particular family of old-world lizards, the Lacertidae (with representatives such as the European Green Lizard, Lacerta viridis and the common Wall Lizard, Podarcis muralis).

The fossil record of amphisbaenians is slim and their evolutionary history clouded with mystery. Previously, a paper published in Nature (Wu et al., 1993) described the taxon Sineoamphisbaena hexatabularis from the Upper Cretaceous of Inner Mongolia, as a stem amphisbaenian, but this conclusion turned out to be quite erroneous (Kearny, 2003).

Fig 2.- My reconstruction of Cryptolacerta hassiaca.

Now, a new Nature paper, written by Johannes Müller and co-workers present Cryptolacerta hassiaca from the Eocene Messel pit in Germany as a new ancestral amphisbaenian (Müller et al., 2011). Cryptolacerta is known from a single specimen consisting of a nearly complete articulated skeleton (missing only the end of the tail). It was small, very lizard-like in appearance but with relatively tiny limbs and a thickened skull. The structure of the skull of Cryptolacerta moreover supports the Lacertidae-Amphisbaenian molecular connection and indicates that skull reinforcement evolved before snake-like body in this particular group of headfirst burrowing reptiles.


References:

Kearny, M. 2003. The phylogenetic position of Sineoamphisbaena hexatabularis reexamined. J. Vert. Paleont. 23, 394-403.

Müller J., Hipsley C.A., Head J.J., Kardjilov N., Hilger A., Wuttke M. & reisz R.R. 2011. Eocene lizard from Germany reveals amphisbaenian origins. Nature 473, 364-367.

Townsend, T.M., Larson, A., Louis, E. & Macey, J.R. 2004. Molecular phylogenetics of Squamata: the position of snakes, amphisbaenians, and dibamids, and the root of the squamate tree. Syst. Biol. 53, 735-757.

Vidal, N. & Hedges, S.B. 2005. The phylogeny of squamate reptiles (lizards, and amphisbaenians) inferred from nine protein-coding genes. C. R. Biol. 328, 1000-1008.

Wu, X.-C. et al. 1993. Oldest known amphisbaenian from the Upper cretaceous of Chinese Inner Mongolia. Nature, 57-59.