Bipedal Cretaceous lizard tracks

These are the oldest lizard tracks in the world…
(if you don’t consider Rotodactylus (Early Triassic) strictly a ‘lizard’ (= squamate). One rotodactylid trackmaker, Cosesaurus, is a tiny lepidosaur).
Figure 1. Bipedal lizard tracks from South Korea in situ.

Figure 1. Bipedal lizard tracks from South Korea in situ. They are tiny.

From the abstract
“Four heteropod lizard trackways discovered in the Hasandong Formation (Aptian-early Albian), South Korea assigned to Sauripes hadongensis, n. ichnogen., n. ichnosp., which represents the oldest lizard tracks in the world. Most tracks are pes tracks that are very small. The pes tracks show “typical” lizard morphology as having curved digit imprints that progressively increase in length from digits I to IV, a smaller digit V that is separated from the other digits by a large interdigital angle. The manus track shows a different morphology from the pes. The predominant pes tracks, the long stride length of pes, narrow trackway width, digitigrade manus and pes prints, and anteriorly oriented long axis of the fourth pedal digit indicate that these trackways were made by lizards running bipedally, suggesting that bipedality was possible early in lizard evolution.”
Actually, the lizard was not running.
Typically in running tracks the prints are very far apart and these tracks are sometimes left toe to right heel.
Figure 2. Original and new tracings of the bipedal lizard tracks from South Korea. PILs are added,

Figure 2. Original and new tracings of the bipedal lizard tracks from South Korea. PILs are added. Manual digit 4 and 5 appear to have shifted.

 The authors did not venture who made the tracks.
They reported, “based on the palaeobiogeographic distribution of facultative extant families, the lizard that produced S. hadongensis tracks could well have been a member of an extinct family or stem members of Iguania, which was present in the Early Cretaceous.”
Actually the closest match among tested taxa
is with Eichstaettisaurus (Fig. 1), a basal member in the lineage of snakes. And this clade is close to the origin of geckos. ReptileEvolutiion.com and the large reptile tree would have been good resources for the authors to use. Lots of lizard pedes were illustrated and scored there.
Figure 3. Originally pictured as a generic lizard (below), here Eichstattsaurus scaled to the track size walks upright.

Figure 3. Originally imagined  as a generic lizard (below), here Eichstattsaurus matched and scaled to the track size walks upright.

 Based on a phylogenetic analysis of the tracks
the closest match in the LRT is with Eichstaettisaurus, so a slightly larger relative made them. Distinct from the skeletal taxon, the trackmaker had a longer p2.1 than 2.1 and pedal digit 1 was quite short. Otherwise a good match in all other regards.
So why walk bipedally?
It was walking, not running, so escape from predation can be ruled out. Elevating the upper torso and head, like a cobra, can be intimidating to rivals, or just offer a better view over local plant life. This sort of flexibility could have helped them get into the trees and then to move to higher branches.
References
Lee H-J, Lee Y-N, Fiorillo AR &  LÃ J-C 2018. Lizards ran bipedally 110 million years ago. Scientific Reports 8: 2617. doi:10.1038/s41598-018-20809-z
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Cornwallius: not a desmostylian, an ancestor to desmostylians

These taxa
are part of the a recent review of mysticete (baleen whale) ancestors you can read about here, here and here.

Cornwallius sookensis (originally Desmostylus sookensis, Hay 1923, Cornwall 1922; Beatty 2006a, b; Early Oligocene, 25 mya; Fig. 1) was originally and traditionally considered a desmostylian (Fig. 3). Here it nests with Cambaytherium (Fig. 2), both basal to anthracobunids like Janjucetus. These taxa have a narrow skull and a deep jugal beneath the squamosal. The nares are anterior, rather than dorsal in location.

Figure 1. Adult Cornwallius look more like desmostylians. Juveniles look more like anthracobunids. Both are descendant taxa.

Figure 1. Adult Cornwallius look more like desmostylians. Juveniles look more like anthracobunids. Both are descendant taxa.

Note the resemblance
(lack of a downturned snout) on the juvenile to Cambaytherium (above). Apparently, neotony produces a straights-snout anthracobunid. Otherwise it evolves to the tusky, droop-snout, desmostylian grade.

Figure 2. Cambaytherium with a an alternate rostrum reversing taphonomic shifts.

Figure 2. Cambaytherium with a an alternate rostrum reversing apparent taphonomic shifts.

Beatty 2006
produced the following cladogram (Fig. 3) in which desmostylians are derived from the Moeritherium/Elephas clade. In the large reptile tree (LRT, 1163 taxa) cambaytheres and desmostylians arise from mesonychids and hippos.

Figure 2. From Beatty 2006b, a phylogeny of desmostylians derived from moeritherium, an aquatic relative of elephants and sirenians (manatees). Actually desmostylians arise from cambaytheres and anthracobunids, arising from hippos and mesonychids. 

Figure 3. From Beatty 2006b, a phylogeny of desmostylians derived from moeritherium, an aquatic relative of elephants and sirenians (manatees). Actually desmostylians arise from cambaytheres and anthracobunids, arising from hippos and mesonychids.

References
Beatty, BL 2006a. Rediscovered specimens of Cornwallius (Mammalia, Desmostylia) from Vancouver Island, British Columbia, Canada. Vertebrate Palaeontology. 1(1):1–6.
Beatty, BL 2006b. Specimens of Cornwallius sookensis (Desmostylia, Mammalia) from Unalaska Island, Alaska. Journal of Vertebrate Paleontology. 26(3):785–87.
Cooper LN, Seiffert ER, Clementz M, Madar SI, Bajpai S, Hussain ST, Thewissen JGM 2014. Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls. PLoS ONE. 9 (10): e109232. doi:10.1371/journal.pone.0109232. PMID 25295875.
Cornwall IE 1922. Notes on the Sooke Formation, Vancouver Island, B.C. Canadian Field Naturalist. 36:121–23.
Hay OP 1923. Characteristics of sundry fossil vertebrates. Pan-American Geologist. 39:101–120.
Kumar K 1991. Anthracobune aijiensis nov. sp. (Mammalia: Proboscidea) from the Subathu Formation, Eocene from NW Himalaya, India”. Geobios. 24 (2): 221–39. doi:10.1016/s0016-6995(91)80010-w. OCLC 4656806310.
Rose, KD et al. (8 other authors) 2014. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications. 5 (5570). doi:10.1038/ncomms6570.

wiki/Cambaytherium
wiki/Cornwallius

Mystacodon: See how far they’ll go to ‘find’ a mysticete ancestor

According to Wikipedia
Mystacodon (Lambert et al. 2017) is a genus of toothed mysticete from the Late Eocene Yumaque Formation of Peru. It is the earliest known member of the Mysticeti, and the second confirmed Eocene mysticete.” Here (Fig. 1) you can compare it to the smaller and more primitive (because it has a bigger pelvis) Maiacetus, to scale. Mystacodon is no mysticete. It’s what a tenrec/odontocete becomes when it gets good at swimming, but not as good as Zeuglodon, which has an even smaller pelvis. We looked at the origin of mysticetes among desmostylians earlier here, here and here. It was first reported here, last October, perhaps too late for the manuscript submission publishing schedule. Even so, whale experts have omitted, overlooked or ignored desmostylians in their quest for mysticete ancestors, and this is what happens.

This is what happens with taxon exclusion.
You get a ‘by default’ nesting, like nesting turtles and Vancleavea with archosaurs or Tetraceratops with therapsids. It also reminds me of when David Hone and Sterling Nesbitt bent over backward to find a mandibular fenestra and an antorbital fossa on pterosaurs in a desperate attempt to prove an invalid hypothesis.

FIgure 1. This toothy whale with a tiny pelvis is Mystcodon, originally promoted as the earliest known mysticete (baleen whale).

FIgure 1. My, what big teeth you have! This toothy whale with a tiny pelvis is Mystcodon, originally promoted as the earliest known mysticete (baleen whale). Note the size and placement of the teeth matching Maiacetus.

And the whale authors got all the publicity they wanted
in this Guardian article with illustrations. Here is a quote from the article:

“Fossil hunters say they have unearthed a missing link in the evolution of baleen whales after digging up the remains of a creature thought to have lived more than 36 million years ago.

The whales, known as mysticeti, sport a bristling collection of sieve-like plates known as baleen that they use to filter water for food. Species include the enormous blue whale, the gray whale and the humpback whale.

But while baleen whales are known to have shared a common ancestor with toothed whales, which are the other major group of modern whales, the path by which the creatures emerged has been somewhat hazily understood. Now researchers say they have discovered the oldest known cousin of modern baleen whales, offering unprecedented insights into their evolution.

“This [split in the family tree] has been dated to about 38 or 39m years ago,” said Olivier Lambert, co-author of the research from the Royal Belgian Institute of Natural Sciences. “The whale we discovered here has been dated to 36.4 [million years ago], so it is only two to three million years younger than this presumed origin.”

From Nature.com:
“This is the fossil that we’ve been waiting for,” says Nick Pyenson, a palaeontologist at the Smithsonian National Museum of Natural History in Washington DC. 

“To determine where M. selenensis fit in the whale family tree, the researchers compared characteristics such as the shape of its skull and pelvic bone to those of other fossil whales. The creature’s flat snout resembles that of modern baleen whales. But its pelvic bone fit more with ancestral whales, complete with areas where the leg bones would typically slot in, says Lambert. “So, we think that this animal still had tiny legs protruding from the body.”

“Lambert and his colleagues think that M. selenensis might have sucked up its prey from the ocean floor. This wasn’t unusual, however, because baleen-whale ancestors around that time sported a wide variety of dental and feeding mechanisms. “There’s big toothed things, there’s little toothed things and there’s toothless things, all at once,” says Uhen. But by around 23 million years ago, all the whales in this group had baleen, and “all these toothy things go away”, he says.”

Mystacodon has a wide flat triangular rostrum…
so does Physeter, the sperm whale (Fig. 3).

Figure 3. Physeter (sperm whale) skull. Note the low, flat, triangular toothless rostrum.

Figure 3. Physeter (sperm whale) skull. Note the low, flat, triangular toothless rostrum.

Workers:
Examine all possible candidates. Don’t exclude relevant taxa. Mystacodon sheds no light on the origin of baleen whales—but it does shed light on the origin of odontocetes.

References
Lambert, O. et al. (seven co-authors) 2017. Earliest Mysticete from the Late Eocene of Peru Sheds New Light on the Origin of Baleen Whales. Current Biology 27:1535–1541.e2 doi:10.1016/j.cub.2017.04.026.

 

New taxa in the lineage of right whales

Tubby right whales
like Eubalaena (Fig. 1) are different from sleek rorquals, like the blue whale (Balaenoptera). Right whales don’t have the huge throat sack that rorquals expand with sea water + krill. Instead longer baleen fringes and huge lower lips filter right whale meals and usually in a horizontal, rather than a vertical, attack formation.

Figure 1. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

Figure 1. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

According to Wikipedia:
“The pygmy right whale (Caperea marginata), a much smaller whale of the Southern Hemisphere, was until recently considered a member of the Family Balaenidae. However, they are not right whales at all, and their taxonomy is presently in doubt. Most recent authors place this species into the monotypic Family Neobalaenidae, but a 2012 study suggests that it is instead the last living member of the Family Cetotheriidae, a family previously considered extinct.”

That 2012 study was by Marx and Fordyce. The large reptile tree (LRT, 1060 taxa) does not support that assignment, perhaps because Marx and Fordyce omitted tenrecs and desmostylians from their whale analysis. At present all cetiotheres in the LRT have straight rostra and mandibles, a far cry from the dipped snout of these taxa. Note the deep baleen in Caperea (Fig. 1). That’s a right whale trait.

Figue 2. Caperea is a transitional taxon between tubby Desmostylus and tubby Eubalaena. Note the tiny manus (flipper). It is neotenous. See text for details. Note the short tail, not much longer than the tail found in Desmostylus.

Figue 2. Caperea is a transitional taxon between tubby Desmostylus and tubby Eubalaena. Note the tiny manus (flipper). It is neotenous. See text for details. Note the short tail, not much longer than the tail found in Desmostylus.

Caperea marginata (The pygmy right whale; Bisconti 2012, Fordyce and Marx 2013) looks like a small blue whale, but has long, inclned ribs, only one lumbar vertbra, and a short tail. The mandible is deep and concave ventrally. Like Eubalaena the lacrimal is deeper than the maxilla. Note the tiny forelimb. The manus has a few extra bones that, when put back together, create a digit 1. Mid-phalanges (3.2, 4.2, 4.3) lost in basal therapsids reappear in this taxon with a netonous tiny manus.

Figure 2. Limusaurus also has four fingers and a scapula with a robust ventral area, like Majungasaurus, but those four fingers are not the same four fingers found in Majungasaurus.

Figure 3. Limusaurus also has an extra digit medial to the other three common to most therapies. We call that digit zero, otherwise found in certain very basal tetrapods only.

We’ve seen this before.
Remember Limusaurus? (If not, check out Fig. 3) That’s the oviraptorid-like theropod with an equally tiny manus provided with an extra medial digit (digit zero). Same thing here provides the reappearance of digit 1, reduced or absent in all ancestors beginning with Mesonyx. And THAT explains the reappearance of manual digit 1 (the thumb) in the right whale, Eubalaena (Fig. 1), the only exception in this clade of thumbless taxa.

Figure x. Desmostylus skull in several views. Note the nasals have a different shape (upper left) than originally traced (lower right). Arrows point to wider mandibles than rostrum.

Figure x. Desmostylus skull in several views. Note the nasals have a different shape (upper left) than originally traced (lower right). Arrows point to wider mandibles than rostrum.

Little things to look for in desmostylians retained by baleen whales

  1. The mandible is wider than the rostrum (Fig. x). That’s where the giant lower lips arise.
  2. A bit of jugal is attached to the front of the squamosal, even when the portion below the orbit is missing.
  3. The reduction of teeth is completed in baleen whales
  4. The ventral portion of the rostrum is visible in lateral view
  5. The anterior tips of the mandibles either have tusks or the alveoli  from which tusks once emerged. Here (Fig. x) the tusks are tiny.
  6. Same with the anterior maxillae, but smaller because those tusks disappear earlier.  Here (Fig. x) the tusks are tiny. Blame it on neotony.
  7. The tail series of Caperea is really quite short (Fig. 2)—and shorter still IF you imagine a former pelvis the size of the one in Desmostylus, now greatly reduced (Fig. 1). And that is a big part of the solution to the lack of a large tail in desmostylians: don’t lengthen the tail…shrink that giant pelvis!!! And blame it on neotony.
Figure 7. Desmostylus jaws with green and blue arrows pointing to buried canine and anterior dentary tusks. Compare to gray whale rostrum in figure 6.

Figure 4. Desmostylus jaws with green and blue arrows pointing to buried canine and anterior dentary tusks. Compare to gray whale rostrum in figure 6.

Figure 8. Gray whale (Eschirctius) anterior rostrum. Green arrow points to the canine alveolus lacking a tooth. Missing mandible teeth would have appeared along anterior rims of the mandibles (blue arrow), as in desmostylians.

Figure 5. Gray whale (Eschirctius) anterior rostrum. Green arrow points to the canine alveolus lacking a tooth. Missing mandible teeth would have appeared along anterior rims of the mandibles (blue arrow), as in desmostylians.

We’ll look at
cetiotheres and rorquals in the next few days.

References
Domning DP, Ray, CE and McKenna, MC 1986. Two new Oligocene desmostylians and a discussion of Tethytherian systematics. Smithsonian Contributions to Paleobiology. 59. pp. 1–56.
Fordyce RE and Marx FG 2013. The pygmy right whale Caperea marginata: the last of the cetotheres. Proceedings of the Royal Society B: Biological Sciences 280(1753):1–6.
Marsh OC 1888. Notice of a new fossil sirenian, from California. American Journal of Science 25(8):94–96.
Reinhart RH 1959. A review of the Sirenia and Desmostylia. University of California Publications in Geological Sciences 36(1):1–146.
Santos G, Parham J and Beatty B 2016. New data on the ontogeny and senescence of Desmostylus (Desmostylia, Mammalia). Journal of Vertebrate Paleontology. doi: 10.1080/02724634.2016.1078344
Tsai C-Hi and Fordyce RE 2015. Ancestor–descendant relationships in evolution: origin of the extant pygmy right whale, Caperea marginata. Biol Lett. 2015 Jan; 11(1): 20140875.

wiki/Caperea
wiki/Desmostylus

The coot: ancestral to chickens, sparrows, parrots and giant stink birds

Fulica atra (Linneaus 1758) is the extant coot, a small water bird with large fleshy feet. Here it nests with Chauna, the screamer, but without such a deadly digit zero. The ascending process of the premaxilla spreads laterally beneath a frontal shield, a decoration on the forehead.

Figure 1. The coot (genus: Fulica) is ancestral to the chicken/parrot clade.

Figure 1. The coot (genus: Fulica) is ancestral to the chicken/parrot clade.

Certainly
an underapprciated bird, given the importance of its transitional morphology between basal storks, like the superficially similar trumpeter Psophia, and the clade of screamers + crakes + chickens + sparrows + parrots + the giant stink birds, Dinornis and Gastornis. The smallest of these became good flyers. The rest never did.

Figure 1. More taxa, updated tree, new clade names.

Figure 1. More taxa, updated tree, new clade names.

This clade
had origins in the Early Cretaceous.

References
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

wiki/Chauna
wiki/Fulica

Dingavis: fangs on a basal bird

Here’s an Early Cretaceous bird
at the base of the Odontornithes (toothed neognaths) with premaxillary and anterior dentary teeth developed into fangs, apparently overlooked by the original authors of Dingavis longimaxilla  (IVPP V20284, O’Connor, Wang and Hu 2016). They were more intrigued by the length of the rostrum and did not appear to delve into the details (Figs. 1,2).

Figure 1. Dingavis longimaxilla in situ nests with Hongshanornis at the base of neognath birds.

Figure 1. Dingavis longimaxilla in situ nests with Hongshanornis at the base of neognath birds. This image is about 3/4 full size, so this is a robin-sized bird.

Maybe they rushed through
Attempting a reconstruction helps the mind sort out some of the problems in crushed fossils such as this one. You can try on one idea after another until one seems to fit. 

Figure 2. Dingavis skull. The large anterior teeth were overlooked in the original description. The naris appears to be quite elongate here.

Figure 2. Dingavis skull. The large anterior teeth were overlooked in the original description. The naris appears to be quite elongate here.

It’s worthwhile to compare Dingavis
to its more plesiomorphic sister, Hongshanornis (Fig. 3). Note the four tiny premaxillary teeth and the others lining the jaws.

That beak tip of Dingavis
is similar by analogy to that of the giant petrel, Macronectes. However, the size differences are too great to draw too much of an analogy.

Figure 3. Hongshanornis skull in situ. Note the four tiny premaxillary teeth, two of which enlarge in Dingavis.

Figure 3. Hongshanornis skull in situ. Note the four tiny premaxillary teeth, two of which enlarge in Dingavis.

Wikipedia reports
“Hongshanornis is a member of the group Hongshanornithidae, to which it lent its name. It is closely related to Longicrusavis, which existed alongside Hongshanornis in the Dawangzhangzi ecosystem” In the LRT these taxa are basal to the Late Cretaceous toothed birds, Hesperornis and Ichthyornis. and so appear to be part of the Odontornithes extending to the Early Cretaceous, shortly after the appearance of Archaeopteryx and other Solnhofen birds.

Figure 4. Hongshanornis in situ with drawing from original paper.

Figure 4. Hongshanornis DNHM D2945, in situ with drawing from original paper. Colors added here.

Wikipedia reports
“In 2016, it was suggested that Dingavis might be cogeneric to the closely related genera Changzuiornis and Juehuaornis [Fig. 5] that might have been found in the same formation, in which case Juehuaornis would have priority.”

Figure 5. Juehuaornis does not have premaxillary teeth, so it is not congeneric with Juehuaornis.

Figure 5. Juehuaornis does not have premaxillary teeth, so it is not congeneric with Juehuaornis.

Lacking large anterior fangs,
Juehuanornis (Fig. 5) is not congeneric with Dingavis. 

References
O’Connor JK, Wang M and Hu H 2016.
A new ornithuromorph (Aves) with an elongate rostrum from the Jehol Biota, and the early evolution of rostralization in birds, Journal of Systematic Palaeontology, DOI: 10.1080/14772019.2015.1129518
Zhou Z and Zhang F 2005. Discovery of an ornithurine bird and its implication for Early Cretaceous avian radiation. PNAS 102(52): 18998-19002. doi:10.1073/pnas.0507106102

wiki/Hongshanornis
wiki/Dingavis

 

Tanycolagreus compared to Yutyrannus

Tanycolagreus topwilsoni (Carpenter et al., 2005, Late Jurassic, TPII 2000-09-29, 3.3m, restored skeleton based on several specimens) was originally considered a coelurid, then a basal tyrannosauroid by several authors. The large reptile tree nests it with the much larger Yutyrannus, but with a relatively longer neck and longer tail.

Figure 1. Tanycolagreus compared to Yutyrannus.

Figure 1. Tanycolagreus compared to Yutyrannus.

Yutyrannus huali (Xu et al. 2012 ZCDM V5000 Zhucheng Dinosaur Museum, Shandong, Lower Cretaceous Yixian Formation) was originally considered a tyrannosauroid theropod likeT-rex. Here it nests as a sister to Tanycolagreus derived from a sister to Sinraptor. Note the lacrimal horns, large three-fingered hand and long torso. Yutyrannus is famous for being a giant feathered theropod, several times larger than the next largest contender.

Figure 2. Yutyrannus skull compared to Tanycolagreus.

Figure 2. Yutyrannus skull compared to Tanycolagreus.

References
Carpenter K, Miles C and Cloward K 2005. New small theropod from the Upper Jurassic Morrison Formation of Wyoming. in Carpenter, K. 2005. The Carnivorous Dinosaurs, Indiana University Press: 23-48
Xu X, Wang K, Zhang K, Ma Q, Xing L, Sullivan C, Hu D, Cheng S, Wang S et al. 2012. A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature 484 (7392): 92–95. doi:10.1038/nature10906. PDF here.

wiki/Yutyrannus
wiki/Tanycolagreus