Sitsqwayk: Not a transitional (toothed/baleen) whale

Sitsqwik cornishorum (Peredo and Uhen 2016, Fig. 1) was originally considered a transitional whale linking toothy aetiotheres to toothless mysticetes (but only in the absence of desmostylians).

Figure 1. Sitsqwayk reconstruction over the ghosted image of Cetotherium. 456 cm represents the 'total body length' according to Peredo and Uhen 2016. The rostrum is restored shorter here to match the mandible.

Figure 1. Sitsqwayk reconstruction over the ghosted image of Cetotherium. 456 cm represents the ‘total body length’ according to Peredo and Uhen 2016. Seems too short. The largely restored rostrum is shorter here to match the mandible.

Taxon exclusion issues
Here testing a wider gamut of mysticete ancestor candidates, Sitsqwayk nests between Cetotherium and two other cetotheres,  Yamatocetus and TokarahiaSitsqwayk has a short rostrum, a convex posterior mandible and a relatively large scapula. The total length was reported as 456 cm, which would make it proportionately much shorter than Cetotherium (ghosted Fig. 1), based on a common scapula size.

Figure 2. Subset of the LRT focusing on mysticetes, including Sitsqwayk, and their predecessors.

Figure 2. Subset of the LRT focusing on mysticetes, including Sitsqwayk, and their mesonychid and desmostylian predecessors. Note that hippos are not artiodactyls, contra tradition.

The term chaeomysticeti (see citation below)
refers to the ‘toothless’ mysticetes. Such a clade is only possible if aetiocetes and Mammalodon are considered mysticetes, but they are not in the large reptile tree (LRT, 1201 taxa) where all mysticetes are toothless and they arise from desmostylians. Mammalodon has teeth, but it is basal to desmostylians, which progressively loose their teeth as they transition to baleen.

Going one step further…
current evidence (i.e. the LRT) indicates that mysticetes should be divided between right whales and all other mysticetes, both with desmostylian ancestors with legs.

It only takes the deletion of a few taxa
to nest odontocetes with mysticetes, or to nest mysticetes with odontocetes in the LRT, due to massive convergence in living whales… as you might expect. That’s why taxon exclusion can be such a problem in phylogenetic analysis. (Keyword: ‘taxon exclusion‘ for dozens of examples of this in this blog).

References
Peredo CM and Uhen MD 2016. A new basal chaeomysticete (Mammalia: Cetacea) from the Late Oligocene Pysht Formation of Washington, USA. Papers in Palaeontology. 2 (4): 533–554.

wiki/Cetotherium
wiki/Sitsqwayk

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What is Fraxinisaura? And what does it look like?

Much missing data here
and incomplete sister taxa likewise missing many bones.

Schoch and Sues 2018
bring us a new Middle Triassic lepidosauromorph reptile with pleurodont tooth implantation. The bones are all disarticulated. They reported, “Phylogenetic analysis recovered Fraxinisaura rozynekae among Lepidosauromorpha and as the sister taxon of the Middle to Late Jurassic Marmoretta oxoniensis. Unfortunately, currently existing character-taxon matrices do not allow confident resolution of the interrelationships of these and other early Mesozoic lepidosauromorph reptiles.”

By contrast
the large reptile tree (LRT, 1200 taxa, Fig. 3) nests Fraxinisaura between Lacertlus and Schoenesmahl, two basal prosquamates not tested by Shoch and Sues. This is where the LRT really shines as it minimizes taxon exclusion problems.

Figure 1. Fraxinisaura as originally reconstructed (below) and as reconstructed here (above) using bone images.

Figure 1. Fraxinisaura as originally reconstructed (below) and as reconstructed here (above) using bone images. Surprisingly, both reconstructions nest Fraxinisaura in the same spot.

First I scored
the Schoch and Sues drawing in the LRT. Then I scored a new reconstruction based on assembling the bone photos in Schoch and Sues 2018.

Surprisingly,
both reconstructions (Fig. 1) nest Fraxinisaura in the same spot in the LRT.

Figure 2. Click to enlarge. Cleaned up reconstruction of the former Bavarisaurus (cololizard at present). Gray areas added based on sister taxa. This is a tritosaur.  Note the large naris bounded ventrally by the maxilla. The ventral pelvis is shallower. I don't understand the pterygoid morphology anteriorly. The upper and lower teeth don't match. That's a red flag, but it is the only data available.

Figure 2. Click to enlarge. Cleaned up reconstruction of the former Bavarisaurus (cololizard at present). Gray areas added based on sister taxa. This is a tritosaur.  Note the large naris bounded ventrally by the maxilla. The ventral pelvis is shallower. I don’t understand the pterygoid morphology anteriorly. The upper and lower teeth don’t match. That’s a red flag, but it is the only data available.

Unfortunately,
Schoch and Sues had too few, and no relevant (closely related) taxa in their taxon list. And the freehand sketch turned out to be not very accurate. They added a darker gray area to the nasals (Fig. 1) because they weren’t ready to accept that the naris might be quite large in Fraxinisaura. I was ready to accept that possibility because Schoenesmahl (Fig. 2) also has a giant naris. Once again, taxon exclusion tends to affect our decisions and sometimes makes us fudge the data.

Figure 2. Subset of the LRT focusing on Fraxinisaura and kin among the prosquamata.

Figure 4. Subset of the LRT focusing on Fraxinisaura and kin among the prosquamata.

Lacertulus is late Permian.
So, it’s no surprise to see Fraxinisaura in the Middle Triassic. Most basal tritosaurs are also Middle Triassic, so it’s no surprise to see prosquamates there, too.

Figure 1. Lacertulus, a basal squamate from the Late Permian

Figure 3. Lacertulus, a basal pro-squamate from the Late Permian.

Fraxinisaura rozynekae (Schoch and Sues 2018, Middle Triassic, SMNS 91547) was originally considered a basal lepidosaurmorph close to Marmoretta. Here it nests between the basal pro-squamates, Lacertulus and Schoenesmahl. The naris is very large. The premaxillary teeth are procumbent and tiny. The humerus and femur are very large and narrow. The original parietal appears to be a clavicle and the parietal is not figured. Scale bars do not produce an identical reconstruction when bones are used instead of freehand drawing.

References
Schoch R and Sues H-D 2018. A new lepidosauromorph reptile from the Middle
Triassic (Ladinian) of Germany and its phylogenetic relationships. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1444619

Multituberculate origins: Two views

A recent paper by Csiki-Sava et al. 2018
described a new multituberculate, Litovoi. The authors also produced a cladogram of multituberculates (Fig. 1).

Long have I wondered
which taxa were considered outgroups for the multituberculates in modern paleo-thinking. Thanks to Csiki-Sava et al. now we know they nested Haramiyavia as the outgroup (Figs. 1, 2).

Or is that solution possible
only due to taxon exclusion?

Figure 1. Cladogram of multituberculate origins and interrelations by Csiki et al. 2018.

Figure 1. Cladogram of multituberculate origins and interrelations by Csiki-Sava et al. 2018.

By contrast
the large reptile tree (LRT, 1201 taxa) nested multis with rodents and plesiadapids (Fig. 2). Haramiyavia nested far distant, as a pre-mammal, not far from Pachygenelus. While the .nex files include all the details, the illustration of skulls (Fiji. 3) compares the two hypotheses of relationships.

Figure 2. Cladogram of multituberculate origins according to the LRT.

Figure 2. Cladogram of multituberculate origins according to the LRT

Taking the skulls from Figure 2
(Fig. 3) one can compare the traditional hypothesis of multituberculate origins with that recovered by the LRT, offering a sort of short hand of all the data scores. One should appear to demonstrate a gradual accumulation of traits. The other should appear to not do so well. Which outgroup lineage appears to have more multituberculate traits in your judgement?

Figure 3. Comparing multituberculate origins: Cziki-Sava et al. vs. LRT.

Figure 3. Comparing multituberculate origins: Cziki-Sava et al. vs. LRT. Gray background taxa are multituberculates. The morphological gap between Haramiyavia and multis is great, much greater than the gap between Paramys and multis.

The closest living relative of long extinct multituberculates,
according to the LRT is Daubentonia, the aye-aye (Figs. 4, 5), once considered a lemur-like primate, but here nesting with extinct Carpolestes and the multis. No other primate, living or extinct (Plesiadapis is also a rodent relative in the LRT), has such a suite of bony traits, including those very large, rodent-like (due to homology) incisors.

Figure 1. Daubentonia was considered a primate for over 150 years. Here it nests with Plesiadapis, rodents and rabbits.

Figure 4. Daubentonia was considered a primate for over 150 years. Here it nests with Plesiadapis, rodents and rabbits.

According to Wikipedia
“The multituberculates existed for about 166 or 183 million years, and are often considered the most successful, diversified, and long-lasting mammals in natural history. They first appeared in the Jurassic, or perhaps even the Triassic, survived the mass extinction in the Cretaceous, and became extinct in the early Oligocene epoch, some 35 million years ago. The oldest known species in the group is Indobaatar zofiae from the Jurassic of India, some 183 million years ago, and the youngest are two species, Ectypodus lovei and an unnamed possible neoplagiaulacid, from the late Eocene/Oligocene Medicine Pole Hills deposits of North Dakota. If gondwanatheres are multituberculates (all tested taxa are not in the LRT), then the clade might have survived even longer into the Colhuehuapian Miocene in South America, in the form of Patagonia peregrine.”

Figure 2. Skeleton of Daubentonia (aye-aye). Like other plesiadapids, it convergences with the lemuroid primates.

Figure 5. Skeleton of Daubentonia (aye-aye). Like other plesiadapids, it convergences with the lemuroid primates.

Employing taxon inclusion,
the LRT presents a heretical and more parsimonious hypothesis of multituberculate origins (Figs 2, 3) that tests Haramiyavia and over 1000 other possible candidates.

To test this hypothesis,
simply add the above suggested relevant taxa to your favorite wide gamut phylogenetic analysis and run. Let me know if your analysis then confirms the LRT—or do you find yet another origin/set of outgroups for the multituberculates? Haramiyavia has very few multi traits, far fewer than rodents and Daubentonia.

References
Csiki-Sava ZVremir MMeng JBrusatte SL and Norell MA 2018. Dome-headed, small-brained island mammal from the Late Cretaceous of Romania. 

https://en.wikipedia.org/wiki/Haramiyavia
https://en.wikipedia.org/wiki/Multituberculata

More turtles with temporal fenestrae

Figure 1. Skull of the basal hard-shell turtle, Baena. Some of these bone IDs and their sutures differ from those from Gaffney 1979. Principally, the gray/red bone is the supratemporal, considered absent by all turtle experts when they do not recognize the pareiasaur origin of the clade.

Figure 1. Skull of the basal hard-shell turtle, Baena. Some of these bone IDs and their sutures differ from those from Gaffney 1979. Principally, the gray/red bone is the supratemporal, considered absent by all turtle experts when they do not recognize the pareiasaur origin of the clade.

Yesterday we looked at several turtles with a lateral temporal fenestra. Today a few more are presented including Baena and Kayentachelys, turtles recently added to the large reptile tree (LRT, 1201 taxa).

Figure 2. Kayentachelys skull with bones colored differently than in the original drawings.

Figure 2. Kayentachelys skull with bones colored differently than in the original drawings.

These two extinct turtles
nest between basalmost forms and extant turtles.

By convergence
several turtle clades (Fig. 3) developed various skull fenestrae, including soft-shell turtles beginning with Arganaceras (not sure if it’s a turtle or not yet) and Odontochelys.

Figure 3. Subset of the large reptile tree (LRT, 1199 taxa) with the addition of three basal turtles

Figure 3. Subset of the large reptile tree (LRT, 1199 taxa) with the addition of three basal turtles. The Mongolochelys/Chubutemys clade did not develop temporal fenestrae. Foxemys and Macrochelys had tentative occipital invagination that extended further with more derived taxa in their respective clades.

Among the most striking of the fenestrated turtle skulls
are the [cryptodire = straight neck in dorsal view, S-curve in lateral view] common Eastern box turtle (genus: Terrapene, Fig. 4) and the [pleurodire = S-curve side neck in dorsal view] matamata (genus: Chelus, Fig. 5). It’s difficult to label these two ‘anapsids’ based on their skull morphology, but that’s the traditional label.

Figure 4. Terrapene, the box turtle, with skull bones colorized. Note the lack of a dermal skull and the appearance of the cranial skull, the braincase.

Figure 4. Terrapene, the box turtle, with skull bones colorized. Note the fenestrated skull. See how colors make bones so much easier to understand. You’ll note many academic papers have been following this trend lately.

Figure 2. Chelus frmbiata, the mata-mata has a temporal fenestra. Not sure if it's a lateral or upper type. Note also the mistake made by Dr. Gaffney in overlooking the squamosal and quadratojugal, and mislabeling the supratemporal.

Figure 5. Chelus frmbiata, the mata-mata has a temporal fenestra. Not sure if it’s a lateral or upper type. Note also the mistake made by Dr. Gaffney in overlooking the squamosal and quadratojugal, and mislabeling the supratemporal. This is one skull you can easily get lost in—if you don’t color the bones. Finally, note the sidesweep of the cervicals in this pleurodire turtle.

References
Gaffney ES 1979. The Jurassic Turtles of North America. Bulletin of the American Museum of Natural History 162(3):91-136.

Basal turtles with a lateral temporal fenestra

Today let’s look at
Glyptops plicatulus (Marsh 1890; AMNH 336; Late Jurassic), an associated skull, shell, and partial skeleton (Fig. 1). Gaffney (1979) reported, “The poor preservation of the skulls precludes a detailed study of the skull roof.” That may be true. Or not. Bones appear to be lost from the temporal regions, but every temporal bone can be identified, just smaller.

Apparently Glyptops had large skull openings
like other turtles. Here the temporal bones were reduced, leaving lateral and suparaoccipital openings, like other turtles. A DGS tracing (Fig. 1) and reconstruction (Fig. 2) provide one solution. Perhaps not the only solution, but one worth considering because no bones are missing here (contra Gaffney 1979).

Figure 1. Glyptops, a basal hard-shell turtle in several views. All data from Gaffney 1979 except the color overlays, which are applied here and used to make the reconstruction in figure 2.

Figure 1. Glyptops, a basal hard-shell turtle in several views. All data from Gaffney 1979 except the color overlays, which are applied here and used to make the reconstruction in figure 2.

According to Gaffney (1979), “their sole unique feature an elongate basisphenoid extending the length of and completely separating the pterygoids.”

Figure 2. Glyptops skull reconstructed from color overlays in figure 1. Note the semi-fenestrated skull mimicking the diapsid configuration.

Figure 2. Glyptops skull reconstructed from color overlays in figure 1. Note the semi-fenestrated skull mimicking the diapsid configuration that Gaffney considered poorly preserved. Gray areas are restored based on sister taxa.

Many traits presage the appearance of traits
in derived turtles, like Terrapene, the Eastern box turtle, by convergence. The two are not directly related to one another, despite sharing several traits. In Glyptops the frontals (lavender) were separated from the parietals (amber) by intervening postfrontals (orange) and postorbitals (aqua) that meet at the midline.

Figure 3. Subset of the large reptile tree (LRT, 1199 taxa) with the addition of three basal turtles

Figure 3. Subset of the large reptile tree (LRT, 1300 taxa) with the addition of three basal turtles

Other turtles that have lateral temporal fenestrae
include the leatherback sea turtle, Dermochelys (Fig. 3, we looked at yesterday), and Meiolania (Fig. 4, now basal to Proganochelys) by convergence.

Figure 2. Skull of Dermochelys adult and juvenile demonstrating the lengthening of the temporal region during maturity. The lateral temporal fenestra appears between the squamosal and quadrate.

Figure 4. From yesterday’s blogpost, the skull of Dermochelys adult and juvenile demonstrating the lengthening of the temporal region during maturity. The lateral temporal fenestra appears between the squamosal and quadrate.

So some turtles are anapsids,
(reptiles that lack temporal openings). Others are not. None are phylogenetic diapsids, despite having large skull openings (Fig. 1) from the top and the sides.

These exceptions remind us
not to define reptiles by their traits (although most of the time this method works well), but rather by their phylogenetic placement (Fig. 3), a method that always works.

Figure 1. Meiolania has a lateral temporal fenestra created by more bone encircling the tympanum (ear drum) at the quadrate. It could be that the top of the qj is actually the fused sq.

Figure 5. Meiolania has a lateral temporal fenestra created by more bone encircling the tympanum (ear drum) at the quadrate, not related to the other temporal openings that start at the back or the bottom of the skull.

Tomorrow,
more laterally fenestrated turtles.

References
Gaffney ES 1979. The Jurassic Turtles of North America. Bulletin of the American Museum of Natural History 162(3):91-136.
Marsh OC 1890. Notice of some extinct Testudinata. American Journal of Science ser. 3, vol. 40, art. 21: 177–179.

The leatherback sea turtle: alone no longer

The leatherback turtle
(genus: Dermochelys) is different from all other sea turtles. It is the only extant genus of the family Dermochelyidae, the sister family to other sea turtles.

Dermochelys coriacea (Vandelli 1761, originally Testudo; Blainville 1816) lacks a bony shell (Fig. 1), replaced by thick, oily, leathery skin. The mouth and esophagus are filled with backward pointing spikes arising from toothess jaws (Fig. 1). Here (Fig. 2) a juvenile skull demonstrates the elevation and lengthening of the postorbital region in the adult.

Figure 2. Dermochelys skeleton, ventral view. In vivo (upper left) and open mouth (lower right).

Figure 1. Dermochelys skeleton, ventral view. In vivo (upper left) and open mouth (lower right).

Note the lack of temporal emargination
in the skull of Dermochelys (Fig. 2). That turns out to not be such a big deal in turtle evolution. The invagination occurred several times in turtles by convergence. This is something one finds out by phylogenetic analysis—if you don’t have an initial bias.

Figure 2. Skull of Dermochelys adult and juvenile demonstrating the lengthening of the temporal region during maturity. The lateral temporal fenestra appears between the squamosal and quadrate.

Figure 2. Skull of Dermochelys adult and juvenile demonstrating the lengthening of the temporal region during maturity. The lateral temporal fenestra appears between the squamosal and quadrate.

Alone no longer.
In the large reptile tree (LRT, 1200 taxa), the freshwater turtle Carettochelys (Fig. 3, 4; Ramsay 1886; 70 cm) nests with Dermochelys. Brinkman, Rabi and Zhao 2017 nested Carettochelys basal to soft shell turtles, unaware that soft shell turtles had a separate origin among small horned pareiasaurs. Like the soft-shell turtle, Trionyx, the soft nose tissue of Carettochelys extends slighly from the skull (Fig. 4) by convergence. Dermochelys (Fig. 1) does not have this proboscis.

Figure 5. Carettochelys skull in two views. Bones colored here.

Figure 3. Carettochelys skull in two views. Bones colored here. Note the long, upturned premaxilla. The invagination of the temporal region is convergent with several other clades of turtles. The supratemporal is orange. The squamosal is lavender. The quadratojugal is a vestige on the posterior maxilla. Compare to figure 2.

The pig-nosed turtle
(genus: Carettochelys) is also unique. It is the only freshwater turtle with flippers. The carapace is not scaly, but leathery (hmm, where have we hear that before?) over bone (Fig. 5).

Despite their differences
Carettochelys and Dermochelys find no closer sisters in the LRT than with each other.

FIgure 1. Carettochelys, the pig-nose turtle, is a freshwater form with flippers, like marine turtles, by convergence.

Figure 4. Carettochelys, the pig-nose turtle, is a freshwater form with flippers, like marine turtles, by convergence.

Why was this not discovered earlier?
Mistaking the supratemporal for the squamosal was only part of the problem. Fusion of the skull bones in turtles (as in birds) gives paleontologists trouble. The dual origin of turtles was not previously considered a possibility.

Figure 1. Carettochelys in 3 views from Digimorph.org and used with permission.

Figure 5. Carettochelys in 3 views from Digimorph.org and used with permission. The leatherback lost its bony carapace.

When workers expand their taxon list
they will recover what the LRT recovers. Until now (Fig. 6), unfortunately, that has not happened.

Figure 3. Subset of the large reptile tree (LRT, 1199 taxa) with the addition of three basal turtles

Figure 6. Subset of the large reptile tree (LRT, 1199 taxa) with the addition of three basal turtles

References
Brinkman D, Rabi M and Zhao L-J 2017. Lower Cretaceous fossils from China shed light on the ancestral body plan of crown soft-shell turtles (Trionychidae, Cryptodira). Nature Scientific Reports 7(6719).
Gaffney ES 1979. Comparative cranial morphology of recent and fossil turtles. Bulletin of the American Museum of Natural History 164(2):65-376.
Ramsay EP 1886. On a new genus and species of fresh water tortoise from the Fly River, New Guinea. Proceedings of the Linnaean Society of New South Wales (2) 1: 158-162.

wiki/Carettochelys
wiki/Dermochelys

Dermochelys and Carettochelys in ReptiliaEvolution.com

 

Kallokibotion: a late-surviving, basal, hard-shell turtle

A recent paper by Pérez-Garcia and Codrea 2018
on the basal, but late-surviving turtle, Kallokibotion bajazidi, (Nopsca 1923a,b) brings us more specimens and more hypotheses of turtle relationships. This taxon has been described as ‘an enigma’, perhaps because all currently known specimens combine Late Triassic traits with a Latest Cretaceous occurrence The visibility of the naris in lateral view goes back to the pre-turtle, Elginia. Transitional taxa, like Meiolania (Fig. 2) and Proganochelys, do not have this trait. Essentially this taxon links the Proganochelys clade to all later hard-shell turtles. (Remember, soft-shell turtles had a separate origin).

Figure 2. Kallokibotion skull in 5 views. Note the twin nares.

Figure 1. Kallokibotion skull in 5 views. Note the twin nares. This skull retains many meiolanid traits.

Gaffney and Meylan 1992 report, “Kallokibotion is a cryptodire because it has the otic trochlea synapomorphy of cryptodires, and it is a member of the Selmacryptodira because it has a posterior pterygoid process under the middle ear. It lacks the posterior temporal emargination synapomorphic of the Daiocryptodira and lies outside that group.”

I’m not going to discuss the suprageneric taxa listed above
because no prior turtle phylogenies recognized the diphyletic nature of soft-shell and hard-shell turtles.

Figure 3. Subset of the large reptile tree (LRT, 1199 taxa) with the addition of three basal turtles

Figure 2. Subset of the large reptile tree (LRT, 1199 taxa) with the addition of three basal turtles

Kallokibotion links
Niolamia and Miolania (Fig. 3 ) with higher turtles, skipping over Proganochelys (Late Triassic, Fig. 4), the traditional baalmost turtle.

 

Figure 3. Kallokibotion compared to Meiolania.

Figure 3. Kallokibotion compared to Meiolania.

Kallokibotion was recognized as a member of Meiolaniformes
in several recently published papers (see Rabi et al., 2013b; Sterli & de la Fuente, 2013; Sterli et al., 2015a, b). Chubutemys is considered a meiolaniform without horns, but workers who proposed this clade did not realize meiolaniids were basalmost hard-shell turtles.

Figure 2. The skull of Proganochelys, a basal turtle without skull invagation and without horns.

Figure 4. The skull of Proganochelys, a basal turtle close to Kallokibation, Note the squamosal and supratemporal and compare those to Kallokibation in  Fig. 1.

Figure 2. Kallokibation carapace and plastron from Gaffney and Melton 1992.

Figure 5. BMNH R4918 specimen of Kallokibation carapace and plastron from Gaffney and Melton 1992. This is the first of the tested taxa that has a short, unarmored tail. The skull was relatively small and unarmored.

Pérez-Garcia and Codrea 2018
discovered new specimens (Fig. 1) that “not only reveal detailed cranial and postcranial elements poorly known until now, refuting previous hypotheses about the anatomy of this taxon, but also allow us to identify numerous hitherto unknown characters.” The new information, “shows Kallokibotion as the sister taxon of the crown Testudines.”

A lot of discussion about crown-group turtles goes out the window
when taxa are included that split hard from soft-shell taxa before turtles had shells. Thus all known turtles, and several non-turtle pareiasaurs, fall under the current definition of crown turtles in the LRT.

Here 
(Fig. 3) Kallokibotion does indeed nest close to the meiolanids and Kayentachelys, but other taxa intervene. The loss of horns and a long armored tail on higher hard-shell turtles, like Kallokibotion, can be attributed to neotony.

Pérez-Garcia and Codrea had no idea what turtles are.
They nest the pre-lepidosauriform, Owenetta, the pareiasaur, Anthodon, the plesiosaur, Simosaurus, and the rhynchocephalian, Sphenodon as progressively more distant outgroup taxa. Throw those out and, except for the meiolanids, their pruned turtle cladogram is similar to the same subset of the LRT.

References
Dyke GJ et al. (20 co-authors) 2014. Thalassodromeus sebesensis—a new name for an old turtle. Comment on ‘Thalassodromeus sebesensis, an out of place and out of time Gondwanan tapejarid pterosaur’, Grellet-Tinner and Codrea. Gondwana Research. doi:10.1016/j.gr.2014.08.004.
Gaffney ES and Meylan PA 1992. The Transylvanian turtle, Kallokibotion, a primitive cryptodire of Cretaceous Age. American Museum Novitates (3040).
Nopcsa F 1923a. On the geological importance of the primitive reptilian fauna of the Uppermost Cretaceous ofHungary; with a description of a new tortoise (Kallokibotion). Quart. Jour. Geol. Soc. 79(1): 100—116.
Pérez-García A and Vlad Codrea 2018. New insights on the anatomy and systematics of Kallokibotion Nopcsa, 1923, the enigmatic uppermost Cretaceous basal turtle (stem Testudines) from Transylvania. Zoological Journal of the Linnean Society. 182(2):419–443. doi:10.1093/zoolinnean/zlx037.
Zhou CF et al. 2015. A sinemydid turtle from the Jehol Biota provides insights into the basal divergence of crown turtles, Scientific Reports (2015). DOI: 10.1038/srep16299

Read more at:
https://phys.org/news/2015-11-insights-family-tree-modern-turtles.html#jCp
wiki/Kallokibotion
https://www.earthmagazine.org/article/trouble-turtles-paleontology-crossroads