Palaeosinopa and Eoarctos: the marsupial to placental 1 transition in the LRT
Yesterday
we looked at the marsupial to placental 2 transition in the large reptile tree (LRT, 2337 taxa).
Today
we’ll look at the less clear marsupial to placental 1 transition in the LRT. Placental 1 taxa include the Carnivora, Primates and Artiodactyla each arising from the other and Carnivora arising from a late-surviving last common ancestor, the marsupial Palaeosinopa (Figs 1, 2) – IF it is a marsupial. In the LRT there is a rapid radiation among placental 1 clades after a more-or-less stepwise evolution preceding this radiation. An alternative is noted below.
The most primitive members of the Carnivora in the LRT are late Eocene Eoarctos and extant Nandinia (Fig 1) the extant palm civet (Fig 2).
One skull of Nandinia
(Fig 1 on white) is quite similar to that of Eoarctos. The other (Fig 1 on black) is not so similar.
These are things you learn to look for when the first and second and third skulls you use in analysis frustrate efforts to link to other taxa.
Figure 1. Pre-placental 1 taxon, Paleosinopa, here compared to basal members of the Carnivora, Eocene Eoarctos and extant Nandinia, the palm civet. See figure 2.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/10/nandinia.palaleosinopa.eoarctos588.gif?w=184″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/10/nandinia.palaleosinopa.eoarctos588.gif?w=584″ class=”size-full wp-image-95088″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/10/nandinia.palaleosinopa.eoarctos588.gif” alt=”Figure 1. Pre-placental 1 taxon, Paleosinopa, here compared to basal members of the Carnivora, Eocene Eoarctos and extant Nandinia, the palm civet. See figure 2.” width=”584″ height=”950″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/10/nandinia.palaleosinopa.eoarctos588.gif?w=584&h=950 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/10/nandinia.palaleosinopa.eoarctos588.gif?w=92&h=150 92w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/10/nandinia.palaleosinopa.eoarctos588.gif?w=184&h=300 184w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/10/nandinia.palaleosinopa.eoarctos588.gif 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. Pre-placental 1 taxon, Paleosinopa, here compared to basal members of the Carnivora, Eocene Eoarctos and extant Nandinia, the palm civet. See figure 2.
Academic textbooks
do not yet recognize two or three separate origins for the clade Placentalia (except for Wortmann 1902). Nor do they yet recognize the hypothesis of phylogenetic miniaturizatiion at the genesis of major and minor clades in the Chordata.
This lack of recognition is largely due to taxon exclusion, which the LRT minimizes.
Figure 6. Palaeosinopa and Sinopa fossil and skeleton both have a long torso, long tail and relatively short legs.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/12/palaeosinopa-sinopa2scale588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/12/palaeosinopa-sinopa2scale588.jpg?w=584″ class=”size-full wp-image-90612″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/12/palaeosinopa-sinopa2scale588.jpg” alt=”Figure 6. Palaeosinopa and Sinopa fossil and skeleton both have a long torso, long tail and relatively short legs.” width=”584″ height=”446″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/12/palaeosinopa-sinopa2scale588.jpg?w=584&h=446 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/12/palaeosinopa-sinopa2scale588.jpg?w=150&h=115 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/12/palaeosinopa-sinopa2scale588.jpg?w=300&h=229 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/12/palaeosinopa-sinopa2scale588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. Palaeosinopa and Sinopa fossil and skeleton both have a long torso, long tail and relatively short legs.
The phenomic study of mammals has proven too difficult –
or not interesting enough – for academics to attempt using a taxon list of 600 synapsids, as in the LRT. Perhaps that’s why academics off-loaded this task to genomic scientists, who (ironically) do not and cannot look at deep time fossil taxa that lack genomic data.
Figure 7. Extant relatives of Eoacrtos include Lemur, Nasua and Nandinia.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2023/06/coatimundi_lemur_palmcivet_invivo588.jpg?w=236″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2023/06/coatimundi_lemur_palmcivet_invivo588.jpg?w=584″ class=”size-full wp-image-78754″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2023/06/coatimundi_lemur_palmcivet_invivo588.jpg” alt=”Figure 7. Extant relatives of Eoacrtos include Lemur, Nasua and Nandinia.” width=”584″ height=”742″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2023/06/coatimundi_lemur_palmcivet_invivo588.jpg?w=584&h=742 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2023/06/coatimundi_lemur_palmcivet_invivo588.jpg?w=118&h=150 118w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2023/06/coatimundi_lemur_palmcivet_invivo588.jpg?w=236&h=300 236w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2023/06/coatimundi_lemur_palmcivet_invivo588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 3. Extant relatives of Eoacrtos include Lemur, Nasua and Nandinia. Note the similarities in proportions between Palaeosinopa and Nandinia, notably that extra long tail.
The African palm civet
“is a nocturnal, largely arboreal mammal that spends most of the time on large branches, among lianas in the canopy of trees. This member of the Carnivora eats fruits and is the most genetically isolated clade member.”
Figure 6. Monodelphls and pups exposed as no pouch is present in this basal placental taxon. Note the tail is not bushy.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/10/monodelphis_and_pups588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/10/monodelphis_and_pups588.jpg?w=584″ class=”size-full wp-image-24463″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/10/monodelphis_and_pups588.jpg” alt=”Figure 6. Monodelphls and pups exposed as no pouch is present in this basal placental taxon. Note the tail is not bushy.” width=”584″ height=”554″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/10/monodelphis_and_pups588.jpg?w=584&h=554 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/10/monodelphis_and_pups588.jpg?w=150&h=142 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/10/monodelphis_and_pups588.jpg?w=300&h=285 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/10/monodelphis_and_pups588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 4. Monodelphls and pups exposed as no pouch is present in this basal placental taxon. Note the tail is not bushy.
If instead Palaeosinopa was a placental,
and other extinct ancestors were placentals, then the last known marsupial, extant Monodelphis kunsi and Monodelphis domestica (Fig 4), both lacking a pouch, would signal the transition from marsupial to placental 1 + 3 taxa.
This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here.
References
wiki/African_palm_civet
PS
The Society of Vertebrate Paleontology abstracts for November 2025 are available online now here: 2025_SVP_Program_Final.pdf
Source: https://pterosaurheresies.wordpress.com/2025/10/30/palaeosinopa-and-eoarctos-the-marsupial-to-placental-1-transition-in-the-lrt/
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