Updated March 23, 2021
with revised scoring that moved Fruitafossor, an edentate-mimic, to a basal relationship with Cifelliodon (Early Cretaceous) and Tachyglossus (extant), two echidnas. Luo and Wible 2005 tested Tachyglossus, but did not know about Cifelliodon, published in 2018.
was a Late Jurassic fossorial digger with universally acknowledged xenarthran (edentate) traits including a long lumbar area that included xenarthran (interlocked) vertebrae. For reasons unknown Luo and Wible 2005 did not test Fruitafossor against another fossorial xenarthran, Peltephilus. Rather the authors compared their digger to an arboreal sloth, Bradypus, among several other taxa, including distinctly different anteaters and armadillos.
Luo and Wible 2005
brought us a small, mostly articulated, rather crushed and incomplete Late Jurassic mammal with simple blunt teeth and digging forelimbs. Fruitafossor windscheffeli (Figs. 1–6) is best represented by a CT scan (Figs. 2–4) and original drawings (Figs. 5, 6) created by Luo and Wible.
The original analysis
nested Fruitafossor between extremely tiny Hadrocodium + Shuotherium and the pre-mammal, Gobiconodon, in a tree topology that does not resemble the topology of the large reptile tree (LRT, 1048 taxa then, 1818+ taxa now). The authors noted Fruitafossor is “not a eutherian, let alone a xenarthran” despite noting Fruitafossor had tubular molars and xenarthran intervertebral articulations, traits otherwise found only in xenarthrans.
the LRT nested Fruitafossor with the horned, armored digging ‘armadillo’ more closely related to Bradypus: Peltephilus. Reconsideration of several traits now nests Fruitafossor with the echindas Cifelliodon and Tachyglossus.
Luo and Wible compared
Fruitafossor to the arboreal and extant Bradypus, but not to the fossorial and extinct Peltephilius.
The retention of the coracoid
in Fruitafossor is a trait found in pre-Therian mammals. Comparisons to echidnas were previously overlooked, but are presently more parsimonious, down to the sprawling limbs. Early Cretaceous Cifelliodon retains derived tubular teeth, precursors to the toothless condition found in extant Tachyglossus. Loss of manual digit 5 in Fruitafossor could be due to taphonomy since the skeleton is somewhat scattered (Fig. 2).
(Luo and Wible 2005; Late Jurassic) was originally considered a digging basal mammal based on the shape of the scapula and sprawling forelimbs. Here Fruitafossor nests as a basal echidna from Colorado, prior to tooth loss. The teeth are blunt, as in xenarthrans, and the four fingers (perhaps five originally) have broad, digging claws with short phalanges. The torso was wider than deep with a long lumbar area that included xenarthran (interlocked) vertebrae. The skeleton was µCT scanned (see above).
Luo Z-X and Wible JR 2005. A late Jurassic digging mammal and early mammal diversification. Science 308:103–107.