Early Eocene Alocodontullum: now an aardvark and anteater ancestor

Rose, Emry and Gingerich 1992 reported,
“A substantially complete skeleton of the early Eocene palaeanodont Alocodontulum atopum from the Bighorn Basin, Wyoming, is described. It is the oldest and most complete known skeleton referable to the family Epoicotheriidae.”

The skull of Epoicotherium, a type of fairy armadillo, is shown below (Fig 4).

Figure 1. The aardvark, Orycteropus, compared to the much smaller and earlier, Alocodontullum, in which the skull was not described, perhaps missing. Note the digging forelimbs. ” data-image-caption=”

Figure 1. The aardvark, Orycteropus, compared to the much smaller and earlier, Alocodontullum, in which the skull was not described, perhaps missing. Note the digging forelimbs.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/05/alocodontullum_skeleton588-1.jpg?w=300″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/05/alocodontullum_skeleton588-1.jpg?w=584″ class=”size-full wp-image-85889″ src=”https://pterosaurheresies.files.wordpress.com/2024/05/alocodontullum_skeleton588-1.jpg?w=584&h=460″ alt=”Figure 1. The aardvark, Orycteropus, compared to the much smaller and earlier, Alocodontullum, in which the skull was not described, perhaps missing. Note the digging forelimbs.” width=”584″ height=”460″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/05/alocodontullum_skeleton588-1.jpg?w=584&h=460 584w, https://pterosaurheresies.files.wordpress.com/2024/05/alocodontullum_skeleton588-1.jpg?w=150&h=118 150w, https://pterosaurheresies.files.wordpress.com/2024/05/alocodontullum_skeleton588-1.jpg?w=300&h=236 300w, https://pterosaurheresies.files.wordpress.com/2024/05/alocodontullum_skeleton588-1.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. The aardvark, Orycteropus, compared to the much smaller and earlier, Alocodontullum, in which the skull was not described, perhaps missing. Note the digging forelimbs.

Here
in the large reptile tree (LRT, 2319 taxa, subset Fig 3) Alocodontulum nests basal to Orycteropus, the extant aardvark (Fig 1), pangolins, anteaters and armadillos.  Rose, Emry and Gingerich mentioned and compared Alocodonulum to Manis, the pangolin, several times, but did not mention ‘aardvark’ or ‘Orycteropus‘.  The Epoicotherium clade of fairy armadillos and kin is a sister to this clade in the LRT.

Dasypus evolved armor by convergence with glyptodonts retained by fairy armadillos.

Figure 2. Alocodontullum the first round reconstruction from several years ago) compared to scale with Metacheiromys, a middle Eocene almost toothless taxon.

Rose, Emry and Gingerich 1992 concluded,
“UM 93740, allocated to Alocodontulurn atopum, is the oldest and most nearly complete
epoicotheriid skeleton known. The skeleton represents an animal about the size of a small
armadillo (Euphractus or Daypus), with a head-body length of roughly 30 cm and a body
weight estimated at approximately 1-2 kg.”

“Alocodontulum is the most fossorially adapted mammal known from the early Eocene of
North America. It was probably armadillo-like in being generally terrestrial (not obviously
subterranean) but a very proficient burrower.”

Earlier these two taxa (Fig 2) nested closer to the basal condylarth Vulpavus.

Figure 3. Subset of the LRT focusing on Xenarthra, the edentates. ” data-image-caption=”

Figure 3. Subset of the LRT focusing on Xenarthra, the edentates.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/05/edentates.clade588.jpg?w=223″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/05/edentates.clade588.jpg?w=584″ class=”size-full wp-image-85891″ src=”https://pterosaurheresies.files.wordpress.com/2024/05/edentates.clade588.jpg?w=584&h=787″ alt=”Figure 3. Subset of the LRT focusing on Xenarthra, the edentates. ” width=”584″ height=”787″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/05/edentates.clade588.jpg?w=584&h=787 584w, https://pterosaurheresies.files.wordpress.com/2024/05/edentates.clade588.jpg?w=111&h=150 111w, https://pterosaurheresies.files.wordpress.com/2024/05/edentates.clade588.jpg?w=223&h=300 223w, https://pterosaurheresies.files.wordpress.com/2024/05/edentates.clade588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 3. Subset of the LRT focusing on Xenarthra, the edentates.

According to Wikipedia,
“Metacheiromys was a small creature, and measured around 45 centimetres (18 in) long. It had long claws and a narrow head similar in shape to that of an armadillo or an anteater (though it was actually related to the modern pangolins).”

Figure 4. Epoicotherium skull in several views. Colors added here.

Rose 2008 reported,
“Despite relatively complete osteological knowledge of several species, the relationships of palaeanodonts remain controversial. They are usually considered to be related to either Xenarthra or Pholidota (or both), but conclusive evidence of their affinities is lacking.”

In the LRT these taxa are ALL related to one another.

Gaudin et al 2009 sought to map out
the phylogeny of the pangolins. Unfortunately they cherry-picked two unrelated outgroup taxa, the palm civet, Nandinia, and the hedgehog, Erinaceus. Correctly they also nested Metacheiromys as a third outgroup taxon.

Note sure why hedgehogs as so popular as outgroup taxa. Clearly hedgehogs are not plesiomorphic relative to bats and/or pangolins.

Alocodontullum atopum
(Rose, Bown and Simons 1978; Rose, Emery and Gingerich 1992; early Eocene, 45 cm in length; UM 93740) is a close relative of Metacheiromys differing chiefly in relative metatarsal and toe lengths and having flat-cusped teeth posterior to the short upper canines with long root. Claws and forelimbs appear ready to dig.

Today’s post is a result of recent housekeeping in the mammal subset of the LRT, correcting freshman errors along the way. In the LRT (subset Fig 3) Xenarthra includes more taxa than university textbooks and academic experts currently indicate.

References
Gaudin TJ, Emry RJ and Wible JR 2009. The phylogeny of living and extinct pangolins (Mammalia, Pholidota) and associated taxa: A morphology based analysis. Journal of Mammal Evolution 16:235–305.
Rose KD, Bown TM and Simons EL 1978. Alocodontulum, a new name for Alocodon Rose, Bown and Simons 1977, non Thulborn, 1973. Journal of Paleontology 52(5):1162.
Rose KD, Emery RJ and Gingerich PD 1992. Skeleton of Alocodontulum atopum, an early Eocene Epoicotheriid (Mammalia, Palaenodonta) from the Bighorn Basin, Wyoming.
Rose KD 2008. Palaeanodonta and Pholidota, chapter 9:135–146.

wiki/Alocodontullum – not yet posted
wiki/Epoicotheriidae