Early Cretaceous stem chameleon/horned lizard

Unnamed stem chameleon (Daza et al. 2016; Early Cretaceous, 1.2cm in length; JZC Bu154; Fig. 1) is a tiny neonate preserved in amber. It also nests basal to horned lizards like Phrynosoma, in the large reptile tree (LRT, 1089 taxa). Note the long, straight hyoid forming the base of the shooting tongue. The split fingers and toes of extant chameleons had not yet developed in this taxon. Found in amber, this newborn lived in a coniferous forest.

Figure 1. The Early Cretaceous stem chameleon/horned lizard found amber. Snout to vent length is less than 11 mm. Much smaller than a human thumbnail.

Figure 1. The Early Cretaceous stem chameleon/horned lizard found amber. Snout to vent length is less than 11 mm. Much smaller than a human thumbnail. Insitu fossil from Daza et al. 2016,  colorized and reconstructed here. At a standard 72 dpi screen resolution, this specimen is shown 10x actual size.

This specimen further cements
the interrelationship of arboreal chameleons and their terrestrial sisters, the horned lizard we looked at earlier with Trioceros and Phyrnosoma in blue of this cladogram (Fig. 2) subset of the LRT.

Figure 3. Subset of the LRT focusing on the neonate stem chameleon/horned lizard.

Figure 2. Subset of the LRT focusing on the neonate stem chameleon/horned lizard.

Figure 6. Phyronosoma, the horned lizard of North America.

Figure 3. Phyronosoma, the horned lizard of North America.

Figure 2. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

Figure 4. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

References
Daza JD et al. 2016. Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards. Sci. Adv. 2016; 2 : e1501080 4 March 2016

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New flightless and giant nyctosaurs: Alcione and Barbaridactylus

Scale bar problems
and a lack of reconstructions in the original paper are issues here.

Longrich, Martill and Andres 2018
bring us news of “a diverse pterosaur assemblage from the late Maastrichtian of Morocco that includes not only Azhdarchidae but the youngest known Pteranodontidae and Nyctosauridae. [This] dramatically increases the diversity of Maastrichtian pterosaurs. At least 3 families —Pteranodontidae, Nyctosauridae, and Azhdarchidae — persisted into the late Maastrichtian. These patterns suggest an abrupt mass extinction of pterosaurs at the K-Pg boundary.”

The authors summary starts off with an invalid statement:
“Pterosaurs were winged cousins of the dinosaurs.”  That was invalidated by Peters 2000, 2007 and ignored every since. We looked at that problem earlier here, here and here in a 3-part series testing all candidates. It’s time to realize that no one will ever find pterosaur kin among the dinos. They’ve already been clearly identified among the lepidosaurs.

The authors failed to include the Maastrictian tupuxuarid
found in southern Texas (Fig. 1; TMM 42489-2) and did not consider the Maastrichtian footprints discovered in 1954 and reexamined in 2018 that include two ctenochasmatids we will look at tomorrow.

TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It's a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

Figure 1. TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It’s a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

Alcione elainus gen. et sp. nov.
The new 1.5x larger nyctosaurid, Alcione elainus, known from disassociated bones including a shorter radius + ulna, a shorter metacarpal 4, a larger femur, and a tiny sternal complex (identified as a ‘sternum’ in the text) only 40 percent the size of a standard nyctosaur sternal complex (if the scale bars are correct). When placed on a reconstruction of a more complete Nyctosaurus (UNSM 93000; Fig. 2), scaled to the humerus, the result produces a likely flightless nyctosaur. Strangely, the authors called this a “small nyctosaur” even though it is half again larger than UNSM 93000. The authors mislabeled the shorter, straighter scapula as a coracoid, and vice versa.

Figure 2. GIF movie of Nyctosaurus and Alcione showing a likely flightless nyctosaur based on the parts preserved.

Figure 2. GIF movie of Nyctosaurus and Alcione showing a likely flightless nyctosaur based on the parts preserved. Three frames change every 5 seconds. The sternum is tiny (assuming the scale bars are correct), the metacarpus and antebrachium are short and the femur is long.

They did not mention the possibility of flightlessness.
They did report, “The abbreviated distal wing elements in Alcione indicate a specialized flight style. The short, robust proportions suggest reduced wingspan and increased wing loading, implying distinct flight mechanics and an ecological shift. Short wings would increase lift-induced drag at low speeds, but reduced wing areas would decrease parasite drag at high speeds, suggesting that Alcione may have been adapted for relatively fast flapping flight compared to other nyctosaurids. Alternatively, reductions in wingspan might represent an adaptation to underwater feeding, i.e., plunge diving of the sort practiced by gannets, tropicbirds, and kingfishers, where smaller wings would reduce drag underwater.”

Not sure why they mentioned
‘distal wing elements’ here. They did not list or discuss distal wing elements elsewhere. Perhaps they meant proximal.

The reconstructed mandible of Alcione
is narrower than the rostrum in UNSM 93000.

Based on the vestigial fingers of UNSM 93000
and the short metacarpus of the new specimen, Alcione might have been the first pterosaur to walk on metacarpal 4, albeit at the very end of the reign of pterosaurs.

Other flightless pterosaurs include:
the basal azhdarchid form the Solnhofen, Jme-Sos 2428 and the Late Jurassic anurognathid PIN 2585/4 from the Sordes slab. They demonstrate that the distal wing elements reduce first. Thus the reconstruction, based on nyctosaur patterns restores a wing that was not volant.

Longrich, Martill and Andres did find a giant nyctosaur
which they named Barbaridactylus grandis based on a large humerus (Fig. 3). The humerus of the more complete UNSM 93000 specimen is 9.5 cm. By comparison the humerus in Barbaridactylus is 22.5 cm. I’m going to trust the text comment that the ulna + radius are 1.3x longer than the humerus. The scale bars indicate about half that length. Similar problem possible in the scapula/coracoid, according to the nyctosaur bauplan.

Figure 3. Barbaridactylus, a giant nyctosaurid. If the wing was like UNSM 93000, then it could fly. If the wing was like Alcione, then it could not. The scale bars did not match the text description on the ulna + radius, so both sizes are shown.

Figure 3. Barbaridactylus, a giant nyctosaurid. If the wing was like UNSM 93000, then it could fly. If the wing was like Alcione, then it could not. The scale bars did not match the text description on the ulna + radius, so both sizes are shown. Sometimes you have to be prepared for the occasional mistake in a published paper.

Other giant nyctosaurs
Earlier and here we noted giant nyctosaurs were flying over the Niobrara Sea (midwest North America) based on a large wing finger with unfused extensor tendon process (YPM 2501) and a large nyctosaur pelvis (KUVP 993; misinterpreted by Bennett (1991, 1992) as belonging to a female Pteranodon). 

No reconstructions were provided
by Longrich, Martill and Andres 2018. Reconstructions and a nyctosaur blueprint might have helped these paleontologists with firsthand access to the specimens discover the issues they missed.

It’s good to know
more pterosaurs made it to the latest Cretaceous.

References
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992.
 Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Longrich NR, Martill DM, Andres B 2018.
Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary. PLoS Biol 16(3): e2001663. https://doi.org/10.1371/journal.pbio.2001663
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. 
The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

Press coverage
Smithsonian
Newswise
PhysOrg

Parrot mimic from the Early Cretaceous

This fossil can be found
(Figs. 1, 2) in the Jeholornis Wikipedia page, labeled Shenzhouraptor. It’s interesting because the rostrum of this Early Cretaceous bird (with impressed feathers) has a downturned tip unlike that of any local taxon. Of course the dentary turns down anteriorly to fit it, as in the convergent parrot, Ara (Fig. 3). I don’t know what the museum number is, nor do I have any reference works that name the genus and species.

Figure 1. What is the museum number and latest generic label for this specimen?

Figure 1. What is the museum number and latest generic label for this specimen?

Here
(subset Fig. 3) it nests with the larger Jeholornis in the large reptile tree (LRT, 1068 taxa). Both are scansoriopterygids.

Figure 2. The Hong Kong specimen attributed to Shenzhouraptor reconstructed from a low-rez image.

Figure 2. The Hong Kong specimen attributed to Shenzhouraptor reconstructed from a low-rez image. If higher resolution is available, please send it along. There is much I am guessing at here. Not sure how to interpret the rostrum based on the presently crappy data. The scale bar is inaccurate.

Figure 3. Scansoriopterygidae includes two Solnhofen birds traditionally labeled Archaeopteryx, but clearly distinct genera. Note, none of these taxa have a styliform bone, as originally figured in Yi qi.

Figure 3. Scansoriopterygidae includes two Solnhofen birds traditionally labeled Archaeopteryx, but clearly distinct genera. Note, none of these taxa have a styliform bone, as originally figured in Yi qi.

By convergence,
The parrot, Ara (below), has features similar to those first appearing in the Hong Kong specimen. Note the deep robust mandible and the ascending jugal, separating the orbit from the conjoined temporal fenestra, making the skull stronger for cracking seeds.

Figure 4. Skull of Ara macao with bones colored.

Figure 4. Skull of Ara macao with bones colored.

References
Looking for them now.

https://en.wikipedia.org/wiki/Jeholornis

Basal mammals: Guess what they evolved to become.

Can you guess
(or do you know) which of these taxa evolved to become a human? a killer whale? a rabbit? a giraffe? a bat? a pangolin?

Figure 1. Can you guess which of these taxa evolved to become a human? a killer whale? a rabbit? a giraffe?

Figure 1. Can you guess which of these taxa evolved to become a human? a killer whale? a rabbit? a giraffe?

H. Onychodectes – basal to all large herbivorous mammals, including giraffes.

G. Maelestes – basal to tenrecs and toothed whales.

F. Tupaia – basal to the gnawing clade including rodents and rabbits.

E. Ptilocercus – basal to Primates, including humans (but note the loss of all premaxillary teeth in this extant taxon).

D. Palaechthon – basal to flying lemurs, bats and pangolins.

C. Monodelphis – basal to all placental mammals.

B. Asioryctes – basal to Monodelphis and all placental mammals.

A. Eomaia – basal to all therian mammals (placentals + marsupials).

These are the basalmost taxa
in various clades of Eutherian (placental) mammals. Not a lot of difference to start (which makes scoring difficult). So much potential at the end. Eomaia goes back to the Early Cretaceous, so it’s not difficult to imagine the radiation of these taxa throughout the Cretaceous.

This falls in line with
the splitting of the African golden mole (Chrysochloris) from its South American sister, Necrolestes, a diversification, migration and split that had to happen before Africa split from South American in the Early Cretaceous.

Sharp-eyed readers
will note the re-identification of bones and teeth in Palaechthon, Ptilocercus and Tupaia. It’s been a long weekend trying to figure out long-standing problems in this portion of the LRT. Some of these taxa were some of the first studied and my naiveté was the source of the earlier disinformation, now corrected. If you see any errors here, please advise and, if valid, repairs will be made.

… and Liaoconodon is not a mammal…

Yesterday we noted that Repenomamus was not a mammal, but nested with the stem- (pre-) mammal tritylodontids, like Pachygenelus. Today Liaoconodon hui (Meng, Wang and Li 2011; IVPP V 16051; early Cretaceous, Aptian, 120 mya), is also not a eutriconodont mammal, but nests between Probainognathus and Pachygnenelus a little deeper into the phylogeny of the Cynodontia in the large reptile tree.

Figure 1. Liaocondon skull traced and reconstructed. In the LRT it most closely resembles that of Probainognathus.

Figure 1. Liaocondon skull traced and reconstructed. In the LRT it most closely resembles that of Probainognathus. Note the enormous size of the temporal fenestrae, the downturned squamosals and postdentary bones, all shared with Probainognathus. 

Liaconodon lacks a coronoid
and the scapula has a ventral glenoid, which are traditional mammal traits. It also has a mammal-like ilium without a posterior process, like a mammal… or a pre-mammal tritylodontid, like Oligokyphus and Kayentatherium. Once again the narrow braincase of Liaconodon, like that of Repenomamus, tells us this is a pre-mammal.

Figure 2. Probainognathus skull(s) in several views along with a pectoral and pelvic girdle.

Figure 2. Probainognathus skull(s) in several views along with a pectoral and pelvic girdle. The lack of a femoral head neck is a trait shared with Liaoconodon. 

Liaconodon lacks large canines
and the lower incisors are quite enlarged. The postorbital bar does not appear to be complete, but the prefrontal, postfrontal and postorbital are still visible and unfused to other bones, as in Probaingnathus.

Figure 3. Liaoconodon in situ.

Figure 3. Liaoconodon in situ. The causals are similar in shape to those of Castrocauda. 

Jin Meng of the AMNH
made a video posted to YouTube describing how ground-breaking it was to find post dentary bones in Liaconodon, which they considered a mammal. Those post-dentary bones are indeed clear and articulated, but par for the clade in pre-mammal cynodonts.

The manus and pes are well preserved
which is something we rarely see around this node. The caudals are nearly identical to those of Castrocauda. The femora were likewise rather short.

It was a good week for finding errors.
As before, we all boggled this one. To those who are toying with the challenge I presented earlier about finding badly nested taxa in the LRT, sorry, you missed this one.

References
Meng J, Wang Y-Q and Li C-K 2011. Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont. Nature 472 (7342): 181–185.

wiki/Liaoconodon

 

Jeholodens and Spinolestes: two new tritylodontids

Revised October 4, 2016 with a shifting of Jeholodens and Spinolestes to the Tritylodontidae, which are pre-mammals arising from Pachygenelus. Tritylodontids replace their molars, something mammals do not do.

The Early Cretaceoous
included the first radiation of basal mammals. The vast majority of these, so far, have been multituberculates, small rodent-like taxa that actually nest with rodents in the large reptile tree. Traditional paleontologists nest multituberculates much more primitively, prior to the Theria (live-bearing mammals) despite their many rodent-like traits, like enlarged incisors followed by a diastema (toothless region) and flat cranial region.

With so many multituberculates
in the Cretaceous, I’m always looking for non-multituberculate mammals from the era.  Repenomamus was a tritylodont, pre-mammal. Vincelestes was a marsupial. Maotherium was an Early Cretaceous basal primate. Liaoconodon, was a pre-tritylodont.  I had high hopes that the next two Early Cretaceous mammals were, as advertised (i.e. something other than multituberculates.)

Another traditional clade of Early Cretaceous mammals
are the eutriconodonts. These include taxa with traditional tooth arcades, but lacking deep canines. Repenomamus is one traditional eutriconodont, but nests in the large reptile tree with Pachygenelus in the tritylodontids. Spinolestes (Fig. 1) and Jeholodens (Fig. 2) are also listed at eutriconodonts, but they nest together in the large reptile tree both as sisters and as derived tritylodontids.

Figure 1. Spinolestes with bones colorized in DGS and both manus and skull reconstructed.

Figure 1. Spinolestes with bones colorized in DGS and both manus and skull reconstructed. Note the tooth pattern recovered here is different than as originally described. If your screen is 72 dpi, then this image is about half again as large as life size.

Spinolestes
has accessory neural articulations, like some shrews do. It also appears to have two sacrals and is otherwise robust overall. The entire foot is present, but scattered. I attempted a reconstruction of the lateral view of the skull based on published clues (Fig. 1).

Figure 2. Jeholodens holotype. Note the tip of the snout is missing, and so are the large anterior premaxillary teeth that characterize this clade.

Figure 2. Jeholodens holotype. Note the tip of the snout is missing, and so are the  anterior premaxillary teeth. If your screen is 72 dpi, then this image is almost twice as large as life size.

Jeholodens jenkinsi
(Ji et al. 1999) was also considered a triconodont, but the tip of the snout is missing. Not as robust as Spinolestes, Jeholodens (Fig. 2) was nevertheless a flat-bodied specimen able to slip into rock cracks. Wikipedia reports the eye was 5 cm across. The true figure is 5 mm.

Ji et al. 1999 reported, “The postcranial skeleton of this new triconodont shows a mosaic of characters, including a primitive pelvic girdle and hindlimb but a very derived pectoral girdle that is closely comparable to those of derived therians. Given the basal position of this taxon in mammalian phylogeny, its derived pectoral girdle indicates that homoplasies (similarities resulting from independent evolution among unrelated lineages) are as common in the postcranial skeleton as they are in the skull and dentition in the evolution of Mesozoic mammals.”

The present analysis indicates
that Jeholodens actually nested with pre-mammal tritylodontids. The naris and small premaxillary teeth provided in the original reconstruction are imagined because that part is broken off the matrix (Fig. 2).

Be wary when you see
the terms ‘mosaic’ and ‘modular’. As we’ve seen before, that usually means the phylogeny is off. Evolution works by a gradual accumulation of traits all over the body, not in a modular or mosaic fashion. Trityodontids look like mammals because they are the proximal outgroup taxon. Multituberculates nest with rodents, with whom they share so many traits.

Figure 3. The tarsus of Jeholodens compared to that of a cynodont, mutituberculate and Didelphis, a marsupial (metatherian).

Figure 3. The tarsus of Jeholodens compared to that of a cynodont, mutituberculate and Didelphis, a marsupial (metatherian). Note that metatarsal 5 is missing in all taxa. Metatarsal 4 becomes a dual metatarsal in Didelphis and most eutherians, but not in Vulpavus, Onychonycteris,

 

Figure 4. Rattus pes. Note distal tarsal 4 only backs up pedal digit 4 and digit 5 rides alongside.

Figure 4. Rattus pes. Note distal tarsal 4 only backs up pedal digit 4 and digit 5 rides alongside.

 

 

 

Using Didelphis for a derived tarsus is a little misleading…
From the Ji et al. 1999 paper (Fig. 3) it looks like Jeholodens has a basal tarsus because distal tarsal 4 is not wide enough to double as a distal tarsal 5, as it does in the marsupial, Didelphis. A quick peek at Rattus (Fig. 4), Vulpavus and Onychonycteris shows that these placental taxa likewise do not widen distal tarsal 4 to back up pedal digit 5. And it is not clear how the Jeholodens tarsus actually stacks up. (Fig. 5). If the tarsus was loose, as it is in bats like Onychonycteris or Pteropus, then it doesn’t necessarily mean the tarsus was primitive, like that of a cynodont. That’s why the overall scores are more important than individual character scores.

Just because something is published in Nature or Science, doesn’t mean it’s necessarily right, as we’ve seen before with Yi, Cartorhynchus, Sclerocormus, Chilesaurus, dinosaur origins. pterosaur origins and turtle origins.

Figure 5. Tarsus of Jeholodens with elements colorized as in other taxa.

Figure 5. Tarsus of Jeholodens with elements colorized as in other taxa.

And while I’m thinking about it,
it may be that clades like “Triconodonta” and “Eutriconodonta” may be junior synonyms for long established taxa, as we looked at earlier here.

References
Ji Q, Luo Z and Ji S. 1999. A Chinese triconodont mammal and mosaic evolution of the mammalian skeleton. Nature 398:326-330. online.

Martin T et al. 2015. A Cretaceous eutriconodont and integument evolution of early mammals. Nature 526:380-384. online.

 

Hypsibema missouriensis – a Late Cretaceous Appalachia duckbill dinosaur

Figure 1. Model of Hypsibema missouriensis, a hadrosaurid dinosaur

Figure 1. Model of Hypsibema missouriensis, a hadrosaurid dinosaur

Hypsibema missouriensis
(Cope 1869; Gilbert and Stewart 1945; Gilbert 1945; Baird and Horner 1979; Darrough et al. 2005; Parris 2006; Campanian, 84-71 mya, Late Cretaceous) is a fairly large hadrosaurid dinosaur discovered in 1942, at what later became known as the Chronister Dinosaur Site near Glen Allen, Missouri. At present this literal pinprick in the map of Missouri is the only site that preserves dinosaur bones.

Figure 2. Where the Hypsibema maxilla chunk came from on the skull of Saurolophus.

Figure 2. Where the Hypsibema maxilla chunk (Figure 3) came from modeled on the skull of Saurolophus.

Small pieces of broken bone and associated caudals and toes
were first discovered when digging a cistern. They had been found about 8 feet (2.4 m) deep imbedded in a black plastic clay. The area is in paleokarst located along downdropped fault grabens over Ordovician carbonates.

Gilmore and Stewart 1945 described a series of Chronister caudal centra (now at the Smithsonian) as sauropod-like, reporting, “The more elongate centra of the Chronister specimen, with the possible exception of Hypsibema crassicauda Cope, and the presence of chevron facets only on the posterior end appear sufficient to show that these vertebral centra do not pertain to a member of the Hadrosauridae.”

First named Neosaurus missouriensis,
the caudals were renamed Parrosaurus missouriensis by Gilmore and Stewart 1945 because “Neosaurus” was preoccupied. The specimen was allied to Hypsibema by Baird and Horner 1979.

Figure 3. Back portion of a Hypsibema maxilla showing tooth root grooves and cheek indention close to jugal.

Figure 3. Back portion of a Hypsibema maxilla showing tooth root grooves and cheek indention close to jugal.

Back in the 1980s
I enjoyed going to the Chronister site with other members of the local fossil club, the Eastern Missouri Society for Paleontoogy. I was lucky enough to find both a maxilla fragment (Fig. 3) and a dromaeosaurid tooth. I remember the horse flies were pesky and  one morning, before the other members got there, I was met by a man with a shot gun who relaxed when I identified myself. A friend found a series of hadrosaur toe bones, each about as big as a man’s hand (sans fingers). The bone was so well preserved you could blow air through the porous surfaces.

References
Baird D and Horner JR 1979. Cretaceous dinosaurs of North Carolina. Brimleyana 2: 1-28.
Cope  ED 1869.
Remarks on Eschrichtius polyporusHypsibema crassicaudaHadrosaurus tripos, and Polydectes biturgidus“. Proceedings of the Academy of Natural Sciences of Philadelphia 21:191-192.
Darrough G; Fix M; Parris D and Granstaff B 2005.
 Journal of Vertebrate Paleontology 25 (3): 49A–50A.
Gilmore CW and Stewart DR 1945. A New Sauropod Dinosaur from the Upper Cretaceous of Missouri. Journal of Paleontology (Society for Sedimentary Geology 19(1): 23–29.
Gilmore CW 1945. Parrosaurus, N. Name, Replacing Neosaurus Gilmore, 1945. Journal of Paleontology (Society for Sedimentary Geology 19 (5): 540.
Parris D. 2006. New Information on the Cretaceous of Missouri. online

wiki/Hypsibema_missouriensis
bolinger county museum of natural history
More info and links