Tiny Deltatheridium leaves the LRT
Known from a partial skull,
the Late Cretaceous (Santonian) cat-like marsupial Deltaheridium (Fig 1), does not have a sufficient number of characters in what remains of this taxon to separate it from its later, larger descendants, Oxyaena and Australohyaena (Fig 2) with which it currently lumps.
More importantly, dropping Deltatheridium from the LRT reduces the MPTs = increases resolution in many other, more distant clades.
Consider pruning scrappy taxa when this happens in your cladogram,
unless your focus is on the scrappy taxon itself.
Figure 1. Deltatheridium skulls, PSS-MAE 132, 133 and AMNH 21706. The back of the skull in the 133 specimen is imagined twice. The elevated posterior rim matches sister taxa like Borhyaena.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/01/deltatheridium_588.jpg?w=111″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/01/deltatheridium_588.jpg?w=380″ tabindex=”0″ role=”button” class=”size-full wp-image-25659″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/01/deltatheridium_588.jpg” alt=”Figure 1. Deltatheridium skulls, PSS-MAE 132, 133 and AMNH 21706.” width=”584″ height=”1573″ />
Figure 1. Deltatheridium skulls, PSS-MAE 132, 133 and AMNH 21706. The back of the skull in the 133 specimen is imagined twice. The elevated posterior rim matches sister taxa like Borhyaena. Note the four molars and three premolars, as in other marsupials.
Sometimes dropping poorly represented taxa like this becomes necessary
because every included taxon affects every other taxon in a cladogram. As more clades converge with one another (this one looks like a cat, civet, tiger and sabertooth) testing more complete taxa becomes more important in lumping and separating, much more distant taxa, surprisingly, as you’ll find when you build your own LRT.
And that’s okay. It’s part of the process.
It’s difficult enough with complete taxa. So why add to a list of problems?
The LRT keeps scrappy taxa in dark red. They don’t disappear completely.
Figure 1. Oligocene Australohyaena to scale with Eocene Oxyaena and Middle Cretaceous, Deltatheridium and Homo sapiens. So, no, Delatheridium was not a marsupial kitten, but a nocturnal adult living each day avoiding dinosaurs.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/australohyaena588.jpg?w=187″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/australohyaena588.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-87450″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/australohyaena588.jpg” alt=”Figure 1. Oligocene Australohyaena to scale with Eocene Oxyaena and Middle Cretaceous, Deltatheridium and Homo sapiens. So, no, Delatheridium was not a marsupial kitten, but a nocturnal adult living each day avoiding dinosaurs. ” width=”584″ height=”939″ />
Figure 2. Oligocene Australohyaena to scale with Eocene Oxyaena and Middle Cretaceous, Deltatheridium and Homo sapiens. So, no, Delatheridium was not a marsupial kitten, but a nocturnal adult living each day avoiding dinosaurs.
If Deltatheridium lived during the time of Oxyaena,
it might have been considered a marsupial kitten based on its tiny size alone. However, Deltatheridium lived when Velociraptor roamed its range. So all Santonian mammals were small and likely nocturnal. Moreover, Deltatheridium had a full complement of adult teeth.
Figure 1. Oxyaena, a traditional creodont. This is a cat-like member of the carnivorous Marsupialia.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/12/oxyaena588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/12/oxyaena588.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-34547″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/12/oxyaena588.jpg” alt=”Figure 1. Oxyaena, a traditional creodont. This is a cat-like member of the carnivorous Marsupialia.” width=”584″ height=”480″ />
Figure 3. Oxyaena, a traditional creodont. This is a cat-like member of the carnivorous Marsupialia. Note the digitigrade manus and pes, contra the Wikipedia description.
Deltatheridium pretrituberculare
(Gregory and Simpson 1926; Late Cretaceous) was traditionally considered basal to Metatheria = Marsupialia based on its ancient age, but here nests as a derived metatherian basal to Oxyaena and Australohyaena (based on chronology). It is known from two partial cat-like skulls (Fig 1).
Figure 4. Manus and pes of Oxyaena. PILs added here are continuous indicating a plantigrade manus and pes.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/oxyaena-manus-pes588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/oxyaena-manus-pes588.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-87458″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/oxyaena-manus-pes588.jpg” alt=”Figure 4. Manus and pes of Oxyaena. PILs added here are continuous indicating a plantigrade manus and pes. ” width=”584″ height=”415″ />
Figure 4. Manus and pes of Oxyaena. PILs added here are for the most part continuous indicating a plantigrade manus and pes.
According to Wikipedia – Oxyaenidae
“Oxyaenidae is a family of extinct carnivorous placental mammals. Traditionally classified in order Creodonta, this group is now classified in its own order Oxyaenodonta within clade Pan-Carnivora in mirorder Ferae.”
Oxyaenidae are Creodonta in the LRT, but in the Marsupialia, not the Placentalia.
“They were superficially cat-like mammals that walked on flat feet, in contrast to modern cats, which walk and run on their toes. Anatomically, characteristic features include a short, broad skull, deep jaws, and teeth designed for crushing rather than shearing, as in the hyaenodonts or modern cats.”
Continuous PILs (parallel interphalangeal lines, Fig 4) mark Oxyaena as plantigrade.
References
Gregory WK and Simpson GG 1926. Cretaceous mammal skulls from Mongolia. American Museum Novitates 225:20pp.
wiki/Deltatheridium
wiki/Oxyaena
wiki/Australohyaena
wiki/Oxyaenidae
Source: https://pterosaurheresies.wordpress.com/2024/07/13/tiny-deltatheridium-leaves-the-lrt/
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