What is Fruitafossor? A basal echidna from Colorado

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.

Fruitafossor
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.

Figure 1. Scapula of Fruitafossor compared to several candidate sisters. Luo and Wible made things a bit more difficult by presenting left and right scapulae. Here they are all left scapulae for ready comparison. There is no doubt that the Fruitafossor scapula looks more like that of Ornithorhynchus.

ºªº Figure 1. Scapula of Fruitafossor compared to several candidate sisters. Luo and Wible made things a bit more difficult by presenting left and right scapulae. In frame 2 they are all left scapulae for ready comparison. There is no doubt that the Fruitafossor scapula was illustrated to look more like that of Ornithorhynchus. Unfortunately the photo data (Fig. 2) does not clearly support that shape. That shape is so important, it needed to be better documented.

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.

Figure 2. Fruitafossor in situ from Digimorph.org and used with permission and here colorized to an uncertain extent.

Figure 2. Fruitafossor in situ from Digimorph.org and used with permission and here colorized to an uncertain extent. All those little white dots could be scattered osteoderms.

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.

Earlier
the LRT nested Fruitafossor with the horned, armored digging ‘armadillo’ more closely related to BradypusPeltephilus. 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.

Figure 5. Several drawings from Zhou and Wible that one must trust for accuracy. The verification data is too fuzzy to validate.

Figure 3. Several drawings from Luo and Wible that one must trust for accuracy. The verification data is too fuzzy to validate. As in other xenarthrans, the ilia actually form a pair of horizontal plates on either side of the long fused and eroded sacrals. Four fingers is a trait shared with Peltephilus. Imagine that rib cage wider and not so deep.

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).

Figure 1. Early Cretaceous Cifelliodon is ancestral to the living echidna, Tachyglossus according to the LRT. The lack of teeth here led to toothlessness in living echidnas. The skull of Tachyglossus is largely fused together, lacks teeth and retains only a tiny lateral temporal fenestra (because the jaws don't move much in this anteater. Compared to Cifelliodon the braincase is greatly expanded, the lateral arches are expanded and the two elements fuse, unlike most mammals.

Figure 4. Early Cretaceous Cifelliodon is ancestral to the living echidna, Tachyglossus according to the LRT. The lack of teeth here led to toothlessness in living echidnas. The skull of Tachyglossus is largely fused together, lacks teeth and retains only a tiny lateral temporal fenestra (because the jaws don’t move much in this anteater. Compared to Cifelliodon the braincase is greatly expanded, the lateral arches are expanded and the two elements fuse, unlike most mammals.

Figure 3. Tachyglossus skeleton, manus and x-rays. Note the perforated pelvis.

Figure 5. Tachyglossus skeleton, manus and x-rays. Note the perforated pelvis.

Fruitafossor windscheffeli
(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).


References
Luo Z-X and Wible JR 2005. A late Jurassic digging mammal and early mammal diversification. Science 308:103–107.

wiki/Fruitafossor

Peltephilus, the horned armadillo, enters the LRT

Updated June 18, 2021
with the realization that the premaxilla had a ventral / palatal exposure as in Holmesina, a taxon added later.

Peltephilus ferox is close to the base of the armadillos and a sister to Holmesina.

Figure 1. Peltephilus skull, manus and pes. There are 3 premolars and 3 molars present, the standard pattern for sister taxa. Extant armadillos have long, narrow rostra with an elongate premaxilla and 7 cone-shaped identical teeth none of which extend below the orbit.  Two species / specimens are shown here. Line art is from Vizcaino and Farina 1997,

Figure 1. Peltephilus skull, manus and pes. There are 3 premolars and 3 molars present, the standard pattern for sister taxa. Extant armadillos have long, narrow rostra with an elongate premaxilla and 7 cone-shaped identical teeth none of which extend below the orbit.  Two species / specimens are shown here. Line art is from Vizcaino and Farina 1997,

According to
Wkiipedia, “Peltephilus ferox (Ameghino 1887‭; 1.5 m long) the horned armadillo, is an extinct species of dog-sized, armadillo xenarthran mammal which first inhabited Argentina during the Oligocene epoch, and became extinct in the Miocene epoch. Notably, the scutes on its head were so developed that they formed horns protecting its eyes. Aside from the horned gophers of North America, it is the only known fossorial horned mammal. Although it had traditionally been perceived as a carnivore because of its large, triangular-shaped teeth, Vizcaino and Farina argued in 1997 that Peltephilus was a herbivore.”

Postcranially
Peltephilus had transverse bands of ossified armor along the back. It had short legs and large claws, ideal for digging or ripping open ant colonies.

References
Ameghino F 1894. Enumeration Synoptique des especes de mammiferes fossiles des formations Eocenes de Patagonie. Boletin de la Academia Nacional de Ciencias en Cordoba (Republica Argentina) 13:259-452
Ameghino F 1897. Mamiferos Cretaceos de la Argentina. Segunda contribucion al conocimiento de la fauna mastologica de las capas con restos de Pyrotherium. – Boletin Instituto Geografico Argentino 18:406-521.
Vizcaino SF and  Farina RA 1997. Diet and locomotion of the armadillo Peltephilus: a new view. Lethaia, 30, 79-86.

wiki/Peltephilus

Look no further for a Xenarthran ancestor: It’s been Barylambda all along.

…and for aardvarks,
like Orycteropus (Fig.1), the relationship to Barylambda (Fig. 2) is even closer (Fig. 3).

Figure 3. Orycterpus, the extant aardvark, is a living sister to Barylambda from the Paleocene.

Figure 1. Orycterpus, the extant aardvark, is a living sister to Barylambda from the Paleocene.

A suitable ancestor
for the odd mammal clade Xenarthra has been long sought. As it turns out, that ancestor (Fig. 2) has been hiding in plain sight for several decades.

Figure 1. Barylambda looks like a large ground sloth for good reason. It is a sister to the direct ancestor and nests at the base of the Xenarthra along with Orycteropus, the aardvark.

Figure 2. Barylambda looks like a large ground sloth for good reason. It is a sister to the direct ancestor and nests at the base of the Xenarthra along with Orycteropus, the aardvark.

Figure 3. Subset of the large reptile tree showing the nesting of Barylambda with Orycteropus and Xenarthra.

Figure 3. Subset of the large reptile tree showing the nesting of Barylambda with Orycteropus and Xenarthra.

When Barylambda was added to the large reptile tree (LRT; Fig. 3) it nested as a sister to Orycteropus and basal to the Xenarthra (sloths, anteaters and armadillos). That should not come as any big surprise, considering how workers have portrayed and described Barylambda as capable of assuming a tripodal posture, like a ground sloth, with its robust tail.

Often compared to ground sloths, Barylambda (Patterson 1933; originally Titanoides, renamed by Patterson 1937CNHM P-14637, a partial skeleton; late Paleocene, 55 mya) now nests with aardvarks, sloths, anteaters and armadillos. Not sure why this relationship has been overlooked or missed for over 75 years. Certainly many have seen the similarity in overall build. Wikipedia describes current uncertain relationships between Xenarthra and other mammal clades. In any case, it’s good to find yet another ancestor for a former enigma clade using a verifiable analysis.

Note the robust build
of Barylambda, the deep tail chevrons, the tiny premaxillary teeth. the out-turned ilia, the low jugals, the lack of large canine-like canine teeth (in females), all traits that point to aardvark and edentate morphologies. No other tested taxa nest closer. Here Barylambda nests next to, but not with, the basal condylarths in the LRT, Onychodectes. Ectoconus and Pantolambda.

Wikipedia describes Barylambda as a genus of herbivorous pantodont mammal the size of a pony, but with five-toed plantigrade hands and feet. The unguals (claws) were not sharp, but small and rounded. Three species are known. We should look for a smaller sister to Barylambda with a longer rostrum in the Paleocene for more direct ancestors to anteaters and armadillos.

The LRT (now 801 taxa) does not recover the same
cladogram topology as O’Leary et al. 2013, which reported, “Our tree suggests that Placentalia first split into Xenarthra and Epitheria.” I don’t find Barylambda in their taxon list. More criticism of that recent paper on mammal relationships can be found here.

A final thought
Barylambda is a big taxon. Evolutionary novelty most often occurs among small taxa. We might expect that Barylambda and Orycterpus AND the members of the Xenarthra are all descendant from a smaller ancestor in the early Paleocene. Or… perhaps more likely, the novelty we see in Orycteropus AND members of the Xenarthra are based on several smaller descendants of Barylambda, some of them armored, starting in the mid Paleocene when Barylambda was probably common and widespread, rather than rare at its genesis.

References
O’Leary, MA et al. 2013. The placental mammal ancestor and the post-K-Pg radiation of  placentals. Science 339:662-667. abstract
Patterson B 1933. A new species of the amblypod Titanoides from western Colorado. American Journal of Science, 25:4 15-425.
Patterson B 1937. A new genus, Barylambda, for Titanoides faberi, Paleocene amblypod. Geological Series, Field Museum of Natural History, 6:229-231. online
Simons EL 1960. The Paleocene Pantodonta. Transactions of the American Philosophical Society, New Series 50(6):1-81

wiki/Barylambda

 

 

 

Glyptodonts: Armored sloths, not giant armadillos.

Today three taxa were added
to the large reptile tree (now 720 taxa, subset Fig. 1):

  1. Bradypus (three-toed sloth)
  2. Dasypus (armadillo)
  3. Glyptotherium (glyptodont)

Wikipedia reports, “Glyptodonts are an extinct subfamily of large, heavily armored armadillos. Unfortunately, Glyptotherium the glyptodont nests with Bradypus, the sloth in the large reptile tree – and, as you’ll see… for good reason.

Figure 1. Mammals with a few edentates added. Here glyptodonts nest with sloths, rather than armadillos, contra traditional studies.

Figure 1. Mammals with a few xenarthans added. Here glyptodonts nest with sloths, rather than armadillos, contra traditional studies.

Bradypus is the long-legged arboreal tree-hanging sloth
with fewer toes. Just imagine where the short-legged ground sloth will nest. This hypothesis of edentate relationships runs counter to tradition, but one look at the skulls (Figs. 1, 2) and you’ll wonder why this hasn’t been noticed before.

Figure 2. Bradypus skull from Digimorph.org, used with permission, colors added to select bones.

Figure 2. Bradypus skull from Digimorph.org, used with permission, colors added to select bones. Compare to the glyptodont skull in figure 3. Darker images bring out lighter details.

Both the sloth and the glyptodont
have deep, narrow, flat-topped skulls with a deep ventral process of the jugal and a very short rostrum. These traits, along with a long list of others, split armadillos + aardvarks from sloths + glyptodonts.

Figure 3. Glyptodon skull with select bones colorized. Compare to the sloth in figure 2 and the armadillo in figure 4.

Figure 3. Glyptodon skull with select bones colorized. Compare to the sloth in figure 2 and the armadillo in figure 4.

Here armadillos nest with
aardvarks, like Orycteropus, a clade that was once accepted under the clade Xenartha. According to Wikipedia, xenarthans have extra vertebral articulations, the lowest metabolic rates among therians, the ischium and sacrum are fused and males have internal testicles. Pangolins were once considered xenarthans, but here nest with basal primates.

Figure 4. Skull of the armadillo Dasypus from Digimorph.org, used with permission. and select bones colorized.

Figure 4. Skull of the armadillo Dasypus from Digimorph.org, used with permission. and select bones colorized.

 

Note the nesting of 
whales (Maiacetus) + tenrecs (Hemicentetes), another clade without external testicles. As a scientist, I’m pleased to discover these interrelationships, but a little surprised that no one has seen this before. If you that has happened already, I will be glad to promote those papers here.

Placental mammals
are showing a basal split between carnivores and other insectivore / herbivore placentals (eutherians).