Kopidodon enters the LRT basal to pangolins

Today
another enigma taxon nests in the LRT.

The Messel pit (Eocene) assemblage
has produced some of the most incredible fossils of completely articulated skeletons of birds and mammals, often with feathers and fur. and, in this case (Fig. 1), small round ears.

Figure 1. One of five complete skeletons of Kopiodon known from the middle Eocene Messel pits. A hand, foot and pelvis are layered to extend the fingers and toes for scoring.

Figure 1. One of five complete skeletons of Kopiodon known from the middle Eocene Messel pits. A hand, foot and pelvis are layered to extend the fingers and toes for scoring.

Kopidodon macrognathus (originally Cryptopithecus macrognathus Wittich 1902; Weitzel 1933/4; Tobien 1969; Naturmuseum Senckenberg; 115cm total length; middle Eocene, 47 mya; Figs. 1, 5) is traditionally considered, “a squirrel-like mammal with large canines” and therefore, somewhat of an enigma taxon.

Here
in the large reptile tree (LRT, 1669+ taxa) Kopidodon nests at the at the base of the pangolins, a sister to Chriacus (Fig. 2) + bats. Kopidodon likely had a Late Jurassic genesis based on the presence of scaled Zhangheotherium in the Early Cretacous. The skull of Kopidodon has a convex profile, like that of another pangolin ancestor, Metachromys (Fig. 3). This helps inform the likely profile of Zhangheotherium, preserved ventrally exposed.

Figure 2. Chriacus and Onychonycteris nest as a sister to the undiscovered bat ancestor and a basal bat. Miniaturization was part of the transition. So was enlargement of the manus. It is still a mystery why the transitional form decided to start flapping.

Figure 2. Chriacus and Onychonycteris nest as sisters to the pangolin clade with Kopoidodon at its base.

Pangolins
llike Manis (Fig. 4) are slow-moving, muscular, tree climbing insectivores. Their hair coalesces to form overlapping scales. For protection pangolins are able to roll into a ball.

Figure 2. Pangolin ancestor Metacheiromys skeleton and skull.

Figure 3. Pangolin ancestor Metacheiromys skeleton and skull, less than half the size of Kopidodon.

Kopidon was a late survivor of a primitively fur covered radiation. 
Hair-scales first appear in Zhangheotherium.

Figure 2. Manis, the Chinese Tree Pangolin along with other views of other pangolins

Figure 4. Manis, the Chinese Tree Pangolin along with other views of other pangolins

Kopidodon
had 26-29 (it varies) presacral vertebrae + 3 sacrals. The foreclaws were taller than wide (similar to arboreal mammals) and larger than the hind claws. The feet were plantigrade. The limbs were heavily muscled and designed for slow movement. The tail vertebrae diminished posteriorly to tiny elongate bones. Stomach contents include fruit and seeds.

Figure 3. Kopiodon skull in situ 2x and reconstructed.

Figure 5. Kopiodon skull in situ 2x and reconstructed. Compare to figure 3.

Kopidodon is traditionally considered a member
of the Cimolesta, the Pantolestidae, and the Paroxyclaenidae, but traditional members do not form monophyletic clades in the LRT.

Wikipedia (German version) reports,
The first description of Kopidodon took place in 1933, the taxonomic position was controversial for a long time.” The original name, Cryptopithecus, reflects that uncertainty as it tentatively allied this taxon with primates. The LRT minimizes taxon exclusion problems by including a wide gamut of taxa.

If this is not a novel hypothesis of interrelationships,
let me know of the original citation so I can promote it.


References
Clemens WA and von Koenigswald W 1993. A new skeleton of Kopidodon macrognathus from the Middle Eocene of Messel and the relationship of paroxyclaenids and pantolestids based on postcranial evidence. Kaupia 3, 1993, S. 57–73.
Koenigswald W von 1983. Skelettfunde von Kopidodon (Condylarthra, Mammalia) aus dem mitteleozänen Ölschiefer der Grube Messel bei Darmstadt. N Jb Geol Paläont Abh 167:1–39.
Koenigswald W von 1992. The arboreal Kopidodon, a relative of primitive hoofed mammals. In: Schaal S, Ziegler W (eds) Messel. An insight into the history of life and of the Earth. Clarendon Press, Oxford, pp 233–237.
Tobien H 1969. Kopidodon (Condylarthra, Mammalia) aus dem Mitteleozän (Lutetium) von Messel bei Darmstadt (Hessen). Notizblätter der hessischen Landesanstalt für Bodenforschung 97, 1969, S. 7–37.
Tobien H 1988. Kopidodon (Condylarthra, Mammalia) aus dem Mitteleozän (Lutetium) von Messel bei Darmstadt (Hessen). = Kopidodon (Condylarthra, Mammalia) from the middle Eocene (Lutetian) of Messel near Darmstadt, Hesse. Notizblatt des Hessischen Landesamtes fuer Bodenforschung zu Wiesbaden 97: 7-37.
Weitzel K 1933. Kopidodon macrognathus Wittich, ein Raubtier aus dem Mitteleozän von Messel. Notizblätter des Vereins für Erdkunde der hessischen geologischen Landesanstalt Darmstadt 14, 1933, S. 81–88
Wittich E 1898, 1902. ein Raubtier aus dem Mitteleozän von Messel. Notizblatt des Vereins für. Erdkunde zu Darmstadt (5)14: 81-88.

Greman/wiki/Kopidodon