Prodinoceras enters the LRT, but not with Dinoceras = Uintatherium

Preface –
This blogpost concludes with notes on placental origins, perhaps more important than Prodinoceras itself.

Prodinoceras means ‘Before Dinoceras‘
a name given to, then synonymized with the six-horned, fanged grazer, Uintatherium (Fig 1) from the Eocene. A traditional ancestor is Late Paleocene, Prodinoceras (Fig 2, 3).

Figure 6. Uintatherium overall. Note the postcranial similarities with Arsinoitherium. ” data-image-caption=”

Figure 6. Uintatherium overall. Note the postcranial similarities with Arsinoitherium.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/08/uintatherium-overall.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/08/uintatherium-overall.jpg?w=584″ class=”size-full wp-image-23662″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/08/uintatherium-overall.jpg” alt=”Figure 6. Uintatherium overall. Note the postcranial similarities with Arsinoitherium.” width=”584″ height=”329″ />

Figure 6. Uintatherium overall. Note the postcranial similarities with Arsinoitherium.

By contrast,
when added to the large reptile tree (LRT, 2324 taxa) Prodinoceras (Fig 3) nests between much smaller coeval taxa like Ectocion cedrus (UALVP 34944, Fig 3) from the Middle Paleocene and Early Paleocene Alcidedorbignya (Fig 3).

Figure 2. Prodinoceras skeleton from Piveteau (1961), after Flerov (1952). Length approximately 2.9 m. ” data-image-caption=”

Figure 2. Prodinoceras skeleton from Piveteau (1961), after Flerov (1952). Length approximately 2.9 m.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/prodinoceras.skeleton588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/prodinoceras.skeleton588.jpg?w=584″ class=”size-full wp-image-89344″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/prodinoceras.skeleton588.jpg” alt=”Figure 2. Prodinoceras skeleton from Piveteau (1961), after Flerov (1952). Length approximately 2.9 m.” width=”584″ height=”235″ />

Figure 2. Prodinoceras skeleton from Piveteau (1961), after Flerov (1952). Length approximately 2.9 m.

Prodinoceras martyr
(Matthew, Granger and Simpson 1929, Late Paleocene, 2.9 m long) is traditionally considered the most basal uintathere. In the LRT it nests among the most primitive placentals, derived from extant Monodelphis sorex (Fig 3), the yellow-sided opossum, a tiny carnivore/insectivore with sabertooth fangs.

Figure 1. Prodinoceras and relatives in the LRT go back to the extant tiny marsupial, Monodelphis sorex, and include Ectocion cedrus, Alcidedorbignya and nearly toothless Metacheiromys and Ernanodon. ” data-image-caption=”

Figure 1. Prodinoceras and relatives in the LRT go back to the extant tiny marsupial, Monodelphis sorex, and include Ectocion cedrus, Alcidedorbignya and nearly toothless Metacheiromys and Ernanodon.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/prodinoceras.relatives588-1.jpg?w=50″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/prodinoceras.relatives588-1.jpg?w=172″ class=”size-full wp-image-89339″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/prodinoceras.relatives588-1.jpg” alt=”Figure 1. Prodinoceras and relatives in the LRT go back to the extant tiny marsupial, Monodelphis sorex, and include Ectocion cedrus, Alcidedorbignya and nearly toothless Metacheiromys and Ernanodon.” width=”584″ height=”3479″ />

Figure 3. Prodinoceras and relatives in the LRT go back to the extant tiny marsupial, Monodelphis sorex (dimidiata), and include Ectocion cedrus, Alcidedorbignya and nearly toothless Metacheiromys and Ernanodon.

This novel clade
(Fig 3) of sabertooth taxa begins with an extant carnivore/insectivore, Monodelphis sorex = M dimidiata, the yellow-sided opossum (Fig 4). All other clade members are larger and not documented after the Eocene.

Phylogenetically
Monodelphis sorex lived alongside dinosaurs in the Cretaceous since a descendant with a six times larger skull, Didelphodon, was found in Late Cretaceous Hell Creek Formation of North America.

Figure 4. Sabertoothed Monodelphis sorex/dimidiata nests at the base of the sabertooth clade in figure 3. ” data-image-caption=”

Figure 4. Sabertoothed Monodelphis sorex/dimidiata nests at the base of the sabertooth clade in figure 3.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/monodelphis_dimidiata588.jpg?w=263″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/monodelphis_dimidiata588.jpg?w=584″ class=”size-full wp-image-89346″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/monodelphis_dimidiata588.jpg” alt=”Figure 4. Sabertoothed Monodelphis sorex/dimidiata nests at the base of the sabertooth clade in figure 3.” width=”584″ height=”665″ />

Figure 4. Sabertoothed Monodelphis sorex/dimidiata nests at the base of the sabertooth clade in figure 3.

Ectocion and Prodinoceras are considered sabertooth herbivores.
Alcidedorbignya was traditionally considered an omnivore or herbivore. Otherwise nearly toothless Metacheiromys and larger, toothier Ernanodon (Fig 3) are traditional pangolin relatives (but not in the LRT).

Perhaps Monodelphis sorex should be granted more dietary and behavioral influence onl its decendants since this little killer is the only clade member with a known diet and habits.

The distribution of this clade
is now restricted to South America. However Ectocion cedrus is from Alberta. Prodinoceras is from Mongolia. Alcidedorbignya is from Bolivia. Metacheiromys is from Wyoming. Ernanodon is from China. So the radiation of this basal placental clade preceded the breakup of Pangaea or was spread via Cretaceous land bridges.

Related taxa
In the LRT extinct herbivorous pantodonts and extant edentates are related to the sabertoothed taxa in figure 3. One distant branch includes Phenacodus which gave rise to sabertoothed Uintatherium and vestigial canine Gobiatherium. Edward Cope rechristened all the New World edentates as Xenarthra, but African Manis is also a clade member in the LRT. Their last common ancestor, Barylambda, is from North America. Again a pre-Atlantic Ocean origin is indicated here.

Reproduction
This sabertoothed clade followed the last common ancestor(s) of all placental1 taxa in the LRT: extant marsupial Monodelphis sorex + Early Paleocene Pucadelphys, These two were basal to a clade that gave rise to Late Cretaceous Didelphodon, and extant dasyurids, Tasmanian devils and Tasmanian wolves, all marsupials.

That means the first placental1 taxon remains unknown,
but likely resembled tiny sabertoothed Monodelphis sorex (Fig 4). That means saberteeth are not odd nor aberrant, but plesiomorphic for this large clade of placentals that includes humans.

Long canines are also found
in extant Nasua (basal to Primates + Artiodactyla + Carnivora) and many creodonts, now all extinct. These include traditional ‘marsupial’ sabertooths, like Thylacosmilus (Fig 5), which now nests after the placental1 transition. This puts all LRT creodonts into the placenatal1 clade.

Note: These taxa redeveloped saberteeth after evolving from small canine ancestors, like Paroodectes (Fig 5).

Like primates, sabertooth creodonts had a postfrontal that contacted the jugal
to form a ring around the orbit.

Figure 5. Creodont sabertooth evolution. Paroodectes, Hapalodecteis (1VPP V2385), Patagosmilus, Thylacosmilus, Barbourofelis. Here a postfrontal is identified in all taxa. ” data-image-caption=”

Figure 5. Creodont sabertooth evolution. Paroodectes, Hapalodecteis (1VPP V2385), Patagosmilus, Thylacosmilus, Barbourofelis. Here a postfrontal is identified in all taxa.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/patagosmilus-thylacosmilus588.jpg?w=63″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/patagosmilus-thylacosmilus588.jpg?w=214″ class=”size-full wp-image-89352″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/10/patagosmilus-thylacosmilus588.jpg” alt=”Figure 5. Creodont sabertooth evolution. Paroodectes, Hapalodecteis (1VPP V2385), Patagosmilus, Thylacosmilus, Barbourofelis. Here a postfrontal is identified in all taxa.” width=”584″ height=”2798″ />

Figure 5. Creodont sabertooth evolution. Paroodectes, Hapalodecteis (1VPP V2385), Patagosmilus, Thylacosmilus, Barbourofelis. Here a postfrontal is identified in all taxa.

As the LRT recovered earlier, the placenta developed 3x.
Placentas developed independently in burrowing golden moles (Placental2) and arboreal gnawing rodents + multitubercates (Placental3).

Figure 2. Callistoe and Hyaenodon skulls. Colors added here. ” data-image-caption=”

Figure 2. Callistoe and Hyaenodon skulls. Colors added here.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/callistoe.skull588.jpg?w=290″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/callistoe.skull588.jpg?w=584″ class=”size-full wp-image-87511″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/callistoe.skull588.jpg” alt=”Figure 2. Callistoe and Hyaenodon skulls. Colors added here.” width=”584″ height=”604″ />

Figure 6. Callistoe and Hyaenodon skulls. Colors added here. Callistoe does not have a ring around the orbit and other traits shared by taxa in figure 5.

Marsupial or Placental?
Suarez et al 2015 nested Thylacosmilus and Patagosmilus with Callistoe (Fig 6) and other borhyaenids, all extinct. The LRT nests these taxa within the Creodonta, the sister taxon to Nasua + Primates + Carnivora and the clade that includes Xenarthra: all placental taxa.

In the LRT that makes the now extinct Creodonta basal placentals.

Basal placentals are currently derived from a monodelphid marsupial, Monodelphis sorex (Figs 3, 4) in the LRT.

According to Smith 2008, writing about Monodelphis sorex:
“Great sexual dimorphism in size with males up to 50% larger than females. Females lack a pouch and possess more mammae than any other mammal (25-27) arranged with five central nipples and the remainder in lateral lines.

No one has seen a female with 25 young.

The species is terrestrial and crepuscular. Occurs in humid Atlantic forest in eastern Paraguay.”

That’s where Africa once butted up, prior to the Atlantic Ocean.

“They considered the species to be an opportunistic generalist feeder with a principally insectivorous diet supplemented with meat and fruit.”

Perhaps helpless babies are secreted in a nest, or hang on nipples, at least at first.

These are notes
on the last marsupial prior to the appearance of placental1 taxa.

These are human ancestors that hid from dinosaurs during the Mesozoic.

References
Cope ED 1882a. Contributions to the history of the Vertebrata of the lower Eocene of Wyoming and New Mexico, made during 1881. Proceedings of the American Philosophical Society: 139-197.
Cope ED 1882e. Note on Eocene Mammalia. American Naturalist 16:522.
Flerov KK 1952. Novye Dinocerata iz Mongolii (New Dinocerata from Mongolia). Doklady Akademii Nauk SSSR 86, 1029-32.
Granger W 1915. A revision of the lower Wasatch and Wind River faunas, Part III: Order Condylarthra, families Phenacodontidae and Meniscotheriidae. Bulletin of the American Museum of Natural History 34:329-361.
Kondrashov P and Agadjanian AK 2012. A nearly complete skeleton of Ernanodon (Mammalia, Palaeanodonta) from Mongolia: morphofunctional analysis. Journal of Vertebrate Paleontology. 32 (5): 983–1001.
Matthew WD, Granger W and Simpson GG 1929. Additions to the fauna of the Gashato Formation of Mongolia. American Museum Noviates 376: 1–12.
Piveteau J (ed.) 1961 Traité de Paléontologie. Tome VI: L’origine des mammifères et les aspects fondamentaux de leur évolution.
Shaw BJ. 2010. The enigmatic anteaters, sloths, and armadillos: elucidating evolutionary relationships among xenarthran families, Ernanodon antelios, and remaining mammals. Dissertation. Portland State University.
Ding S 1979. A new edentate from the Paleocene of Guandong. Vertebrata PalAsiatica 17:57-64.
Smith P 2008. Red-sided short-tailed opossum Monodelphis sorex – Mammals of Paraguay 26:1–8.
Suarez C et al (4 co-authors) 2015. Insights into the Neotropics prior to the Great American Biotic Interchange: new evidence of mammalian predators from the Miocene of Northern Colombia. Journal of Vertebrate Paleontology. 36 (1): e1029581. doi:10.1080/02724634.2015.1029581.
Ting S, Wang B and Tong Y-S 2005. The type specimen of Ernanodon antelios. Journal of Vertebrate Paleontology 25(3):729-731.

wiki/Ectocion
wiki/Prodinoceas
wiki/Metacheiromys
wiki/Ernanodon