Was the AMNH Tanytrachelos ‘with child’?

Tanytrachelos ahynis (Olsen 1979, holotype AMNH 7496; holotype Fig. 1) Latest Triassic, 200 mya, was derived from Macrocnemus and was a sister to Langobardisaurus and Tanystropheus. All are tritosaur lepidosaurs in the lineage of the terrestrial ancestors of pterosaurs, the Fenestrasauria… all ultimately derived from an earlier sister to late-surviving Huehuecuetzpalli and Tijubina.

Figure 1. AMNH 7496 holotype of Tanytrachelos with original tracing from Olsen 1979. DGS colors added.

Figure 1. AMNH 7496 holotype of Tanytrachelos with original tracing from Olsen 1979. DGS colors added.

The AMNH specimen
(Fig. 1) preserved in ventral exposure, appears to have two halves of a leathery eggshell and an ‘exploded’ embryo, best described as several dozen tiny bones that should not be there, unless, perhaps this was a gravid adult… or something else, like gastroliths, undigested prey… hard to tell. In any case, some of the pectoral bones also have new identities here.

Figure 5. Hypothetical Tanystropheus embryo compared to Dinocephalosaurus embryo.

Figure 2. Hypothetical Tanystropheus embryo compared to Dinocephalosaurus embryo. These are the sorts and sizes of bones one should look for in any maternal Tanytrachelos.

Figure 1. Tanytrachelos hopping to match Gwyneddichnium tracks (see figure 2).

Figure 3. Tanytrachelos hopping to match Gwyneddichnium tracks (see figure 2).

Distinct from Langobardisaurus,
Tanytrachelos has twelve cervicals, but none were gracile. The posterior cervical ribs had large heads that kept the rods far from each centrum. Heterotopic bones were present. These appear to be elongated chevrons, as in Tanystropheus. Rare hopping prints (Fig. 2) match the size and shape of Tanytrachelos pedes.

langobardisaurus-pectoral-girdle

Figure 4. The sternal complex of several other tritosaurs. Tanytrachelos is closer to Tanystropheus, not quite like any of these related taxa, but all are informative.

The elliptical sternum
of Tanytrachelos was wide, as in Langobardisaurus (Fig. 3), but the clavicle remained gracile, as in Huehuecuetzpalli (Fig. 3). The humerus was slightly bowed. Metacarpal I aligned with the others. Metatarsal III was the longest. Digit III was the longest as in Langobardisaurus tonelloi.


References
Olsen PE 1979. A new aquatic eosuchian from the Newark Supergroup Late Triassic-Early Jurassic) of North Carolina and Virginia. Postilla 176: 1-14.
Smith AC 2011. Description of Tanytrachelos ahynis and its implications for the phylogeny of Protorosauria. PhD dissertation. Virginia Polytechnic Institute and State University.

 

SVP 2018: New Mammalodon relative with marine worm bores

Shipps, Peredo and Pyenson 2018 report
on a Late Oligocene mammalodontid, the first from the Northern Hemisphere. “The skull and teeth of this specimen bear boreholes from bone-eating Osedax worms, providing valuable information on the taphonomy of the specimen. Critically, this specimen preserves intact ear bones and several teeth.”

Osedax is marine worm.
According to Wikipedia, “The worms bore into the bones of whale carcasses to reach enclosed lipids, on which they rely for sustenance.”

Figue 1. Mammalodon nests within the clade Anthracobune basal to desmostylians and mysticetes.

Figue 1. Mammalodon nests within the clade Anthracobune basal to desmostylians and mysticetes.

Mammalodon (Fig. 1) is indeed in the lineage of mysticete whales, but several nodes distant (Fig. 2) in the large reptile tree. It is related to Janjucetus and Anthracobune, basal to desmostylians, not far from hippos. Desmostylians are also found along the Pacific rim, so this appearance of an ancestor in Washington state is expected. All are mesonychids, not ungulates.

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 predecessors.

References
Shipps BK, Peredo CM and Pyenson ND 2018. An unexpected Northerner with burrowed bones: a new mammalodontid (Mysticeti) from the Pacific Northwest with Osedax bores provides insight into Oligocene marine taphonomy and mysticete evolution. SVP abstracts.

wiki/Osedax
wiki/Janjucetus
wiki/Mammalodon
wiki/Anthracobune

 

Fish nibbles on Pteranodon metacarpal

Figure 1. Fish teeth compared to grazed Pteranodon metacarpal

Figure 1. Fish teeth compared to grazed Pteranodon metacarpal

Ehret and Harrell 2018
bring us news from Alabama of two distinct sets of tooth marks on a Pteranodon (Fig. 2) metacarpal (Fig. 1). They report:

“The Pteranodon specimen exhibits serrated teeth marks on the surface of the bone and a second set of larger, unserrated teeth marks unlike those of any contemporary shark species. These feeding traces compare favorably with the tooth spacing and morphology of Squalicorax kaupi, and a small to moderate-sized saurodontid fish, such as Saurodon or Saurocephalus, respectively. In both instances, feeding traces appear to be scavenging events due to the lack of any healing or bone remodeling. The specimen represents a pterosaur that either fell into marine waters or was washed out from nearshore areas and then scavenged by both a chondrichthyan and osteichthyan.”

“Many fossils from late Cretaceous Alabama appear to have been nibbled by sharks, including sea turtles and dinosaurs, which are often ‘covered in predation marks,’ says Ehret.”

NatGeo publicized the find by talking to some pterosaur experts, “Pterosaurs actually had a lot of meat on their skeletons,” says Michael Habib, a pterosaur expert at the University of Southern California who was not involved with the latest find. “They were not the skinny animals often depicted in films and art. The flight muscles in particular would have made a great meal.”

Pterosaur metacarpals,
like all metacarpals, actually are sinewy and have little to no associated muscle.

Habib adds,
“Pteranodon also inhabited this coastal environment during the late Cretaceous, making a living snatching smaller fish from the shark-filled waters. Pterosaurs could float, but being less buoyant than birds, they probably didn’t sit on the surface for long. Some species, including Pteranodon, did likely plunge into the water for prey. “They could then quickly take back off from the surface. But these diving pterosaurs might have been vulnerable to sharks just after they entered the water,” he says.

M. Witton concluded,
“It’s nice to know what species were interacting in this way.”

Ehret corrected the pterosaur experts,
“It’s also possible that the animal died near the shore and was scavenged when it washed out to sea.”

Figure 3. Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs.

Figure 2 Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs.

Contra Habib’s statement
Pteranodon was at least as buoyant as a pelican. It has been widely known for over a century that pterosaur bones are thinner than bird bones and Pteranodon metacarpals, in particular, were hollow like pontoons (Fig. 2).

Ultimately
the bite marks represent curiosity, not predation, a point understood by Ehret and Harrell.

References
Ehret DJ and Harrell TL Jr. 2018. Feeding traces of a Pteranodon (Reptilia: Pterosauria) bone from the late Cretaceous (Campanian) Mooreville Chalk in Alabama, USA. Palaios 33(9):414–418.

www.natgeo.com/

Tanystropheus: aquatic? or terrestrial?

Added September 21, 2020:
Think about a bubble net, as in humpback whales, coming form the long, dead=air storage vessel that is that elongate trachea. That long neck rotating like an inverted cone to surround confused fish just above the jaws.

Beard and Furrer 2017 conclude (or do they?)
that Tanystropheus (Figs. 1–3) was likely terrestrial.

From the abstract
“The Middle Triassic protorosaur Tanystropheus has been considered as both a terrestrial and aquatic taxon based on several lines of biomechanical and distributional evidence, but determining conclusively which habitat was most likely has remained problematic. The preservation of Tanystropheus was found to be more similar to Macrocnemus than Serpianosaurus implying carcasses of Tanystropheus originated in terrestrial or at least marginal and near-shore, shallow marine settings. That these were also the most probable habitats in life is supported by the relatively lower number of Tanystropheus (and also Macrocnemus) compared to Serpianosaurus.”

Tanystropheus underwater among tall crinoids and small squids.

Figure 1. Tanystropheus in a vertical strike elevating the neck and raising its blood pressure in order to keep circulation around its brain and another system to keep blood from pooling in its hind limb and tail.

Unfortunately,
Tanystropheus was not a protorosaur, nor a member of the Archosauromorpha. It was a tritosaur lepidosaur as taxon inclusion would have informed the authors.

Tanystropheus and kin going back to Huehuecuetzpalli.

Figure 2. Tanystropheus and kin going back to Huehuecuetzpalli.

Unfortunately,
the smaller Tanystropheus considered a juvenile by the authors was probably a different genus, based on a long list of distinct traits, including its distinct teeth. Moreover the authors did not realize that several large putative Tanystropheus specimens have distinct skull morphologies that are not congeneric (Fig. 2). But all that is beside the point…

Figure 2. Tanystropheus with skull reconstructions based on two specimens, exemplar i and exemplar m.

Figure 3. Tanystropheus with skull reconstructions based on two specimens, exemplar i and exemplar m.

The authors report:
“An alternative aquatic lifestyle has also been suggested for Tanystropheus (Tschanz 1988). The main argument is the supposed inflexibility of the neck due to the elongated vertebrae and bundled cervical ribs that prevented all but a horizontal position (Tschanz 1988; Renesto 2005).”

Or any aquatic position,
including vertical (Fig. 1). The authors do cite the hooks from squid suckers found in the stomach region (Wild 1973; Fig. 1) and other prior hypotheses, then describe the taphonomy of the skeletons. The authors cite trackway data matched to Tanystropheus, (Fig. 3) ignoring the fact that even sea turtles leave trackways on beaches when they lay eggs.

Figure 3. Tanystropheus specimens matched to Synaptichnium tracks. The match is good in each case, except for one toe or the other.

Figure 3. Tanystropheus specimens matched to Synaptichnium tracks. The match is good in each case, except for one toe in each trackway. So, is this good enough? Or is this cause for dismissal?

Did the authors test the tracks?
No. But that is done here (Fig. 3). In each case there is a pretty good match—except for one toe in each case. The manus and pes have been scaled to match the tracks and thus are not matched to the scale bars which are for the tracks alone. Even so, the scale for the trackmakers’ extremities is a pretty good match! The case is not rock solid, but pretty good, that big and small tanystropheids made those Synaptichnium tracks.

Taphonomy 
The journey from the biosphere to the lithosphere was investigated. The terrestrial Ticinosuchus, a type of archosauriform, was discovered in these beds along with the aquatic Serpianosaurus, a type of pachypleurosaur, according to the authors (a basal thalattosaur in the large reptile tree). So was the tritosaur lepidosaur, Macrocnemus. The authors wondered if the taphonomy of Tanystropheus would be more similar to the terrestrial or the aquatic taxa. Wild (1973) listed and illustrated  over a dozen specimens of Tanstropheus in various stages of completeness and articulation. The water depth of fossil deposition was estimated between 30 and 130m with anoxic bottom conditions. So ALL the specimens were transported horizontally and vertically. Importantly, fragmentary skeletons of Tanystropheus were excluded from this study. From the remaining data the authors compiled articulation and completeness scores.

Why did they throw out competing data?
We’ve seen this before with Hone and Benton (2007, 2008). Given that they used only the more complete specimens (and who knows how many incomplete specimens were never collected), the authors report Tanystropheus specimens exhibited 0-58% articulation and 36–97% completeness. Larger specimens tended to be more complete. The authors also note that Serpianosaurus alone lacks obvious features that promoted buoyancy, like hollow cervicals in Tanystropheus. The authors cite Brand et al. 2003, who noted “lizard skin in water formed a limp but durable bag containing the bones” during water transport.

The authors conclude
“Tanystropheus langobardicus at least died in, but probably also lived in a terrestrial or near-shore marine setting.” The presence of squid hooks in the stomach “does not necessarily preclude a more-normal niche in shallow water.” 

‘Near shore marine’ = aquatic.
So the authors conclusion is no conclusion at all. Contra their headline, they did not ‘determine’ anything. It could have been on the beach, or in shallow water. Is the marine iguana (Amblyrhynchus cristatus) aquatic? or terrestrial? What would you say if you only found its skeleton? Or its footprints?

The good evidence continues to be
the stomach contents as the best evidence for life style (feeding niche) for the giant forms. Let the smaller ones feed in shallower waters. Let both give birth and warm up on land, like marine iguanas.

References
Bassani F 1886. Sui Fossili e sull’ età degli schisti bituminosi triasici di Besano in Lombardia. Atti della Società Italiana di Scienze Naturali 19:15–72.
Beard SR and Furrer 2017. Land or water: using taphonomic models to determine the lifestyle of the Triassic protorosaur Tanystropheus (Diapsida, Archosauromorpha). Palaeobiodiversity and Palaeoenvironments (advance online publication) DOI: https://doi.org/10.1007/s12549-017-0299-7
https://link.springer.com/article/10.1007/s12549-017-0299-7
Diedrich C 2008. Millions of reptile tracks—Early to Middle Triassic carbonate tidal flat migration bridges of Central Europe—reptile immigration into the Germanic Basin. Palaeogeography, Palaeoclimatology, Palaeoecology, 259, 410–423.
Haubold HA 1983. Archosaur evidence in the Buntsandstein (Lower Triassic). Acta Palaeontologica Polonica, 28, 123–132.
Li C 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
Meyer H von 1847–55. Die saurier des Muschelkalkes mit rücksicht auf die saurier aus Buntem Sanstein und Keuper; pp. 1-167 in Zur fauna der Vorwelt, zweite Abteilung. Frankfurt.
Nosotti S 2007. Tanystropheus longobardicus (Reptilia, Protorosauria: Reinterpretations of the anatomy based on new specimens from the Middle Triassic of Besano (Lombardy, Northern Italy). Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, Vol. XXXV – Fascicolo III, pp. 1-88
Peyer B 1931. Tanystropheus longobardicus Bass sp. Die Triasfauna der Tessiner Kalkalpen. Abhandlungen Schweizerische Paläontologie Gesellschaft 50:5-110.
Rieppel O, Jiang D-Y, Fraser NC, Hao W-C, Motani R, Sun Y-L & Sun ZY 2010. Tanystropheus cf. T. longobardicus from the early Late Triassic of Guizhou Province, southwestern China. Journal of Vertebrate Paleontology 30(4):1082-1089.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus (Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-162 plus plates.

wiki/Tanystropheus

Wukongopterus – with a broken leg

Pterosaur fossils can get pretty messed up over 150 million years. Most of that happens during their lifetime or shortly thereafter as they sink into sediments.

Wukongopterus (IVPP V15113 , Wang et al. 2009) is a not-quite complete specimen that preserves a broken leg (Fig. 1). The Daohugou Bed of the Tiaojishan Formation was originally described as Early Cretaceous, but is now dated to the Middle/Late Jurassic boundary. This makes more sense with regard to phylogenetic order.

Figure 1. Wukongopterus with a broken tibia (in pink).

Figure 1. Wukongopterus with a broken tibia (in pink). It looks like the tibia was kept in place by tendons and dermis after the break, whether before or after death. Compare the broken tibia to the unbroken one. Even the foot was twisted medial to lateral.

References

Wang X, Kellner AWA, Jiang S and Meng X 2009. An unusual long-tailed pterosaur with elongated neck from western Liaoning of China. Anais da Academia Brasileira de Ciências 81 (4): 793–812.

wiki/Wukongopterus