Middle Jurassic moonrat: Asfaltomylos patagonicus

Ever since the LRT nested multiberculates within Glires,
we’ve been looking for non-multituberculate members of Glires (rats, rabbits, tree shrews, etc.) from the Jurassic to support that novel hypothesis. Here’s one.

Martin and Rauhut 2005
redescribed the mandible and teeth belonging to Asfaltomylos (Rauhut et al. 2002; Fig. 1) famous for being the first Jurassic mammal from South America and for apparently lacking a canine and incisors.

The question:
Is this an egg-laying monotreme (clade: Prototheria)? That’s what both Rauhut et al. 2002 and Martin and Rauhut 2005 thought based on tooth shape and a post-dentary groove in the medial dentary. They also excluded taxa listed below (and shown in figure 1). Such bias is a too common fault in traditional paleontology, as long time readers are well aware.

Figure 1. Asfaltomylos (MPEF-PV 1671) is a tiny mandible with teeth from in Jurassic strata in South America. Note the shape of the posterior premolar and how it relates to the giant posterior premolar in Carpolestes. The canine is tall. Not sure if Asfaltomylos had large incisors. Either way it does not matter, based on comparisons to Echinosorex and Erinaceus, the living moonrat and hedgehog.

Figure 1. Asfaltomylos (MPEF-PV 1671) is a tiny mandible with teeth from in Jurassic strata in South America. Note the shape of the posterior premolar and how it relates to the giant posterior premolar in Carpolestes. The canine is tall. Not sure if Asfaltomylos had large incisors. Either way it does not matter, based on comparisons to Echinosorex and Erinaceus, the living moonrat and hedgehog. Only the posterior molar in Erinaceus looks like the two molars in Asfaltomylos, separated in time by 166 million years.

Based primarily on tooth morphology,
Rauhut et al. 2002 considered Asfaltomylos a member of the Australosphenida, a clade of southern Jurassic mammals that is said to convergently evolve tribosphenic molars with northern mammals and probably gave rise to monotremes. Their taxon restricted cladogram nested Asfaltomylos between Shuotherium (Fig. 2) and several untested taxa leading to several platypus-like  taxa (including genus: Ornithorhynchus; Fig. 3.)

Question for you, dear readers:
Do the mandibles of Asfaltomylos (Fig. 1) and Shuotherium (Fig. 2) resemble one another? They should, given their proximity in the Rauhut et al. and Martin and Rauhut cladograms. If you think they don’t look similar, perhaps we need to expand the taxon list.

Figure 2. Medial view of Shuotherium. The last premolar is similar to the first molar, the coronoid process is tiny and the retroarticular process is absent, all distinct from Asfaltomylos (Fig. 1).

Figure 2. Medial view of Shuotherium. The last premolar is similar to the first molar, the coronoid process is tiny and the retroarticular process is absent, all distinct from Asfaltomylos (Fig. 1).

As a test, let’s add all the mammals in the LRT.
When we do, and based on very few mandible characters, Asfaltomylos foregoes the Prototheria and nests with derived members of Glires, derived from moonrats, the only members of Glires that sometimes do not have large gnawing incisors (yet another reversal).

Only the posterior molar
in the hedgehog, Erinaceus (Fig. 1), looks like the two molars in Asfaltomylos, separated in time by 166 million years. The premolar is nearly identical.

Moonrats
(Fig. 4) have an appropriately primitive appearance, and are different from other members of Glires in being chiefly carnivorous.

Rougier et al. 2007
considered Henosferus another member of the clade ‘Australosphenida’. With its  complete dental formula on a low profile mandible, Henosferous (Fig. x) nests with other basalmost therians, like Morganucodon (Fig. 3) in the LRT, not close to Asfaltomylos. So members of the invalidated clade ‘Australosphenida’ are polyphyletic in the LRT.

Figure 1. Henosferus mandible restored by Rougier et al. 2005 from several broken specimens.

Figure x. Henosferus mandible restored by Rougier et al. 2005 from several broken specimens.

Phylogenetic miniaturization and neotony
answer the problems posed by the low number of molars and the retention of the postdentary trough in Asfaltomylos. As you may recall, mammals recapitulate their phylogeny during ontogeny and Asfaltomylos matured at an earlier stage of development due to its small size.

Tooth morphology is something else to be ware of in phylogenetic analyses.
As an example, whale teeth devolved from multi-cusped in a square in their four-limbed terrestrial ancestors, to multi-cusped in a row in archaeocetes with flukes, to simple cones and toothlessness in derived odontocetes.

Figure 1. Brasilodon compared to Kuehneotherium, Akidolestes and Ornithorhynchus, the living platypus.

Figure 3. Brasilodon compared to Kuehneotherium, Akidolestes and Ornithorhynchus, the living platypus, and Monodelphis, a living tree opossum.

The problem is,
the high coronoid process and retroarticular (angular) process of Asfaltomylos are not found in Ornithorhynchus (Fig. 3) nor in other Prototheres in the large reptile tree (LRT, 1631+ taxa, Fig. 2). Prototheria are notable for their long rostra, lots of teeth and low coronoid process, traits that don’t match the  Asfaltomylos mandible. The medial surface of Asfaltomylos does include a dentary trough in which tiny posterior jaws bones would soon evolve to become ear bones… except that happens by convergence in highly derived arboreal mammals, like multituberculates, that experience that reversal in the auditory region, to the chagrin of Jurassic mammal workers worldwide.

Figure 3. Echinosorex, the extant moonrat, looks like an opossum, but nests with Deinogalerix in the large reptile tree.

Figure 4. Echinosorex, the extant moonrat, looks like an opossum, but nests with Deinogalerix in the large reptile tree.

In the LRT
Asfaltomylos nests with the moonrat Echinosorex, not far from Carpolestes (Fig. 1), a plesiadapiform in the LRT. 

Here’s a thought:
Take a look at that tall, narrow, posterior premolar in Asfaltomylos. That’s what turns into a similar posterior premolar in moonrats and hedgehogs. That’s what turns into a large cutting premolar in Carpolestes and multituberculates. 

Figure 1. Subset of the LRT focusing on Glires and subclades within.

Figure 5. Subset of the LRT focusing on Glires and subclades within. Moonrats and hedgehogs are not too far from Carpolestes and arboreal taxa like aye-aye.

Once again, the LRT shows why it is so important
to test all enigma taxa against a wide gamut of taxa, like the LRT. The LRT minimizes bias in the choice of the inclusion set of taxa. The number of characters for the mandible in the LRT comes down to less than dozen. Tooth cusp characters are largely omitted. So character count is, once again, shown to be not nearly as important, contra the opinions of workers who ask for more characters to no advantage.


References
Martin T and Rauhut OWM 2005. Mandible and dentition of Asfaltomylos patagonicus (Australosphenida, Mammalia) and the evolution of tribosphenic teeth. Journal of Vertebrate Paleontology 25(2):414–425.
Rauhut OWM, Martin T Ortiz-Jaureguizar E and Puerta P 2002. A Jurassic mammal from South America. Nature 416:165–168.
Rougier, GW, Martinelli AG, Forasiepi AM and Novacek M J 2007. New Jurassic mammals from Patagonia, Argentina : a reappraisal of australosphenidan morphology and interrelationships. American Museum novitates, no. 3566. online here.

wiki/Asfaltomylos

https://pterosaurheresies.wordpress.com-henosferus/

SVP abstracts – the Skye pterosaur

Martin-Silverstone, Unwin and Barrett  2019 bring us
news of a new Middle Jurrasic Scottish pterosaur: the Skye pterosaur.

From the abstract
“The Middle Jurassic was a critical time in pterosaur evolution – a series of major morphological innovations underpinned radiations by, successively, rhamphorhynchids, basal monofenestratans, and pterodactyloids. Frustratingly, however, this interval is also one of the most sparsely sampled parts of the pterosaur fossil record, consisting almost exclusively of isolated fragmentary remains.”

…other than all the many complete Jianchangnathus, Changchengopeterus, Pterorhynchus, Darwinopterus, and Dorygnathus specimens, that is. Why are these three pterosaur experts pretending these wonderfully preserved taxa don’t exist?

Figure 1. Skye pterosaur from traced from in situ specimens found online.

Figure 1. Skye pterosaur in ventral view traced from in situ specimen photos found online with limbs duplicated graphically. This preliminary data was enough to nest it in the LPT better than three PhDs with a set of µCT scans hampered by their much smaller unresolved pterosaur cladogram.

Martin-Silverstone et al. continue:
“Here we report on the most complete individual found to date, a three-dimensionally
 preserved, partial pterosaur skeleton recovered in 2006 from the Bathonian-aged Kilmaluag Formation, near Elgol, Isle of Skye, Scotland. Micro-CT scanning, segmentation, and 3D-reconstruction using Avizo has revealed multiple elements of the axial column, fore-, and hind limbs, many of which were fully embedded within the matrix and inaccessible via traditional preparation and imaging techniques.”

“Unique features of the coracoid distinguish the Skye pterosaur from all other species, indicating that it represents a new taxon.”
“The new specimen was included in phylogenetic analysis that was conducted using maximum parsimony in PAUP on a data matrix consisting of 61 taxa scored for 136 morphological characters. This analysis generated 544,320 MPTs.
OMG!!! What a confession!! That is a sign of a  lousy cladogram!!
“The 50% majority rule tree places the Skye taxon as a basal monofenestratan in a clade with Darwinopterus, Wukongopterus, and, for the first time, Allkaruen, which was previously identified as non-monofenestratan.
The LPT confirms the nesting of the Skye pterosaur with Darwinopterus, but closer to Jianchangnathus and Pterorhynchus (Fig. 2). In the LPT, Alkaruen nested basal to the ctenochasmatid, Pterodaustro. Details on that here.
Figure 3. Subset of the LPT showing the nesting of the Skye pterosaur from available data (Fig. 1).

Figure 2. Subset of the LPT showing the nesting of the Skye pterosaur from available data (Fig. 1). This is a terminal clade with no known descendants, contra Martin-Silverstone, Unwin and Barrett.

The Skye pterosaur, one of the earliest, most complete records for Monofenestrata, provides critical new insights into pterosaur evolution.”
The large pterosaur tree (LPT, 241 taxa; subset Fig. 2) once again finds no evidence for a monophyletic Monofenestrata and the entire LPT is resolved. If the Martin-Silverstone, Unwin and Barrett team added 180 taxa they would also find no evidence for a monophyletic Monofenestrata and their resolution would increase.
“The distal end of the Skye pterosaur’s scapula is expanded and articulated with the vertebral column, a feature shared with other basal mononfenestratans. Comparisons across Pterosauria show that this type of bracing was far more widespread than previously realized and seemingly present in many clades, with the exception of basal-most (Late Triassic) forms. The development of a notarium, providing additional stability and support, is confined to derived and often large and giant species and forms only part of the complex evolutionary history of the scapulo-vertebral contact.”
They could have simply said, a notarium is present. Instead they took a paragraph to do so, omitting many other traits that could have been mentioned. When scientific data is published, the authors of that data open their work for criticism and assistance. In that way errors are corrected and omissions are included.
Googling ‘Skye pterosaur’ results in several hits
including this classified ad from a year ago seeking a paleo student to work with a set of pterosaur expert PhDs. Hope it was a fulfilling experience for that student.
“Closing in January 2019: We seek a student with experience in studying and describing fossil and/or living animal specimens, comparative vertebrate anatomy, a broad background in biological and/or geological sciences, and experience or a willingness to learn statistical and CT techniques. As the student will be working with a large team, teamwork skills and a collaborative mindset are essential.” palass.org/careers

References
Martin-Silverstone E, Unwin DM and Barrett PM  2019. A new, three-dimensionally preserved monofenestratan pterosaur form the Middle Jurassic of Scotland and the complex evolutionary history of the scapulo-vertebrael articulation. Journal of Vertebrate Paleontology abstracts.

Upper Jurassic tidal flat pterosaur tracks from Poland

Note:
The following is from an unedited manuscript accepted for publication and pre-published online. The editors note: copyediting may change the contents by the time this is officially published. Not sure why the editors are going this route, except for comment and validation. Hope this gets back to them for the help it offers.

Elgh et al. 2019 report,
“In this paper, we report newly discovered, well-preserved pterosaur track material.”

The authors mistakenly report, 
“Intermediates between most of these states can be seen in the non-pterodactyloid
groups most closely related to the pterodactyloids, e.g. the rhamphorhynchids and wukongopterids” 

No, tiny dorygnathids and scaphognathids are transitional taxa when more taxa are added in the large pterosaur tree (LPT, 238 taxa). Wukongopterids are a sterile lineage, otherwise known as a dead end. There are 4 convergent pterodactyloid-grade clades. All these are recovered by adding taxa without bias.

The authors mistakenly report,
“As noted previously, digit V differs greatly between non-pterodactyloids and pterodactyloids. In non-pterodactyloids this digit is long and supported the uropatagium.”

No, the long and unique fifth digit is found in tanystropheids, langobardisaurids and fenestrasaurs like Cosesaurus and Sharovipteryx. No pterosaur fossil shows uropatagial support. This is a myth. Exceptionally, and for hind wing gliding, each uropatagium extends nearly to the tip of digit 5 in Sharovipteryx.

The authors mistakenly report, 
“Furthermore, pterodactyloids lost their teeth in several lineages, something not seen among nonpterodactyloids.” 

Adding taxa recovers four pterodactyloid-grade clades, as shown by LPT. Two arise from distinct lineages within Dorygnathus. Two others arise from tiny descendants of Scaphognathus. One clade from each lineage produces toothless taxa.

The authors mistakenly report,
“The non-wing bearing digits are much shorter and increase in length from IIII.” 

Typically, yes, but not always. Sometimes all three small phalanges are sub-equal in length.

The authors mistakenly report, 
“Their phalangeal formula is 2-3-4-4, since the wing finger ungual is lost.”

Not true. I have shown many examples of a wing ungual.

The authors mistakenly report, 
“The pes has five digits with a phalangeal formula of 2-3-4-5-2. The penultimate phalanx is elongated in digits I-IV.”

Not true. Pterodaustro (Fig. 1) and several other beach coming pterosaurs do not have elongate penultimate pedal phalanges. The authors cite the invalidated paper by Unwin 1996, rather than Peters 2011, which compared and showed many examples of pterosaur feet and tracks.

Figure 1. A selection of ctenochasmatid feet. Note the short penultimate phalanges (green).

Figure 1. A selection of ctenochasmatid feet from Peters 2011. Note the short penultimate phalanges (green) are not longer than the longest phalanx in series.

The authors mistakenly report,
“The wukongopterids, being the non-pterodactyloid group(s) most closely related to the pterodactyloids have, as with many characters, an intermediate state with a fifth digit that is shorter than in other non-pterodactyloids but longer than in pterodactyloids.”

Not true. Wukongopterids generally have a larger pedal digit 5 than in many other basal pterosaurs and are not related to derived pterosaurs despite several traits that converge. As mentioned above, phylogenetic miniaturization occurred 4 times in the ancestry of the 4 pterodactyloid-grade pterosaurs.

The authors mistakenly report, 
“It is unclear how the fifth digit functioned in terrestrial locomotion in all groups of pterosaurs.” 

Not true. Peters 2000 and 2011 showed exactly how pedal digit 5 was used with comparable tracks and hypothetical perching situations.

To eliminate considering the above issues, the authors report,
“no exhaustive morphometrical methods compare pes and manus impressions with anatomical details to pes and manus body fossils have been made. The most creative attempt to match pes anatomy to tracks by Peters (2011) regrettably introduces too many speculations to be of use in this study.”

That’s how it works, folks. Like Hone and Benton, 2007 and 2009, many pterosaur workers prefer to toss out data that challenges traditions. On the plus side: doing so ensures publication in the present academic climate.

No longer requiring personal examination
of fossils, the authors report, “The Anurognathus ammoni described by Döderlein (1923) was measured using an image of the specimen published by David Hone online (here). The A. ammoni described by Bennett (2007b) was measured using an image published on the pterosaur.net website (here).”

Elgh et al. present several images of
pedal impressions, but they are isolated, so there is no confirmation of left or right identity. This is critical as some pterosaurs have a longest pedal digit 2, while others have a longest pedal digit 3. Others are sub equal. When three ungual bases are collinear most of the time those are digits 2–4, but not always. One Rhamphorhynchus specimen and Nemicolopterus goes the other way.

That statistic has implications for Elgh et al.
who identify four traced fossils with unguals aligned with digit 3 often the longest.

Below
I employ the first photo and first drawing by Elgin et al. (Fig. 2) and find an overlooked pedal morphology (in color overlay) and a strong similarity to an Early Cretaceous Beipiaopterus, a taxon not mentioned in the authors’ current text. Having a pedal digit 1 similar in length to the other three medial toes is very rare, so many other candidates are readily eliminated leaving this one and few to no others. Beipiaopterus nests in the LPT between a series of dorygnathids and a series of pre-azhdarchids, some of them from Solnhofen sediments.

Figure 1. Left and center images from Elgh et al. Colors and pes of Beipiaopterus added for comparison.

Figure 2. Left and center images from Elgh et al. Colors and pes of Beipiaopterus added for comparison.

Elgh et al. made no effort
at locating pedal pads or joints that correspond to pad/joint patterns in pterosaur pedes. By contrast, coloring the track reveals a typical pterosaur pes with a typical pad/joint pattern, but atypical phalanx lengths.

No pterosaur pedes in Peters 2011 are a perfect match,
but Early Cretaceous Beipaiopterus comes close.

Note that Elgh et al. ignored the curved impression
made by the elongate digit 5—because they were married to traditional paradigms, instead of going with the data as is.

I can only wish, at this point,
that future pterosaur workers add more precision to their studies and consider all possibilities… rejecting traditional hypotheses that cannot be validated, while embracing hypotheses that reflect reality.


References
unedited manuscript accepted for publication:
Elgh E, Pieńkowski G and Niedźwiedzki G 2019. Pterosaur track assemblages from the Upper Jurassic (lower Kimmeridgian) intertidal deposits of Poland: Linking ichnites to potential trackmakers, Palaeogeography, Palaeoclimatology, Palaeoecology, https://doi.org/10.1016/j.palaeo.2019.05.016
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18, 114-141.
Unwin DM 1996. Pterosaur tracks and the terrestrial ability of pterosaurs. Lethaia 29, 373-386.

Mesozoic mammals: Two views

Smith 2011 reported,
at the beginning of the Eocene, 55mya, “the diversity of certain mammal groups exploded.” These modern mammals”, according to Smith, ‘ consist of rodents, lagomorphs, perissodactyls, artiodactyls, cetaceans, primates, carnivorans and bats. Although these eight groups represent 83% of the extant mammal species diversity, their ancestors are still unknown. A short overview of the knowledge and recent progress on this research is here presented on the basis of Belgian studies and expeditions, especially in India and China.’

Contra the claims of Smith 2011
in the large reptile tree (LRT, 1354 taxa, subsets Figs. 2–4) prototherians are known from the late Triassic (Fig. 1). Both metatherians and eutherians are known from the Middle Jurassic. Many non-mammal cynodonts survived throughout the Mesozoic. In addition, the ancestors of every included taxon are known back to Devonian tetrapods.

Noteworthy facts after an LRT review (Fig. 1):

  1. All known and tested Mesozoic mammals (Fig. 1) are either small arboreal taxa or small burrowing taxa (out of sight of marauding theropods).
  2. All Mesozoic monotremes are more primitive than Ornithorhynchus and Tachyglossus (both extant).
  3. All Mesozoic marsupials are more primitive than or include Vintana (Late Cretaceous).
  4. All Mesozoic placentals are more primitive than Onychodectes (Paleocene).
Figure 1. Select basal cynodonts and mammals set chronologically. The divergence times for placentals (Eutheria), marsupials (Metatheria) and monotremes (Mammalia) are estimated here.

Figure 1. Select basal cynodonts and mammals set chronologically. The divergence times for placentals (Eutheria), marsupials (Metatheria) and monotremes (Mammalia) are estimated here.

Given those parameters
we are able to rethink which mammals were coeval with dinosaurs back on phylogenetic bracketing (= if derived taxa are present, primitive taxa must have been present, too).

Smith reports, “The earliest known mammals are about as old as the earliest dinosaurs and appeared in the fossil record during the late Trias around two hundred and twenty million years ago with genera such as Sinoconodon (pre-mammal in the LRT), Morganucodon (basal therian in the LRT) and Hadrocodium (basal therian in the LRT). However, the earliest placental mammals (Eutheria) were not known before the Early Cretaceous. Eomaia scansoria (not eutherian in the LRT) from the Barremian of Liaoning Province, China is the oldest definite placental and is dated from a hundred and thirty million years ago.”

Mesozoic Prototherians

  1. All included fossil taxa are Mesozoic. Two others are extant (Fig. 2).
Figure 2. Mesozoic prototherians + Megazostrodon, the last common ancestor of all mammals. Only two taxa (gray) are post-Cretaceous.

Figure 2. Mesozoic prototherians + Megazostrodon, the last common ancestor of all mammals. Only two taxa (gray) are post-Cretaceous.

Mesozoic Metatherians (Marsupials)

  1. Derived Vincelestes is Early Cretaceous, which means Monodelphis and Chironectes were present in the Jurassic.
  2. Derived Didelphodon is Late Cretaceous, which means sisters to Thylacinus through Borhyaena were also present in the Mesozoic.
  3. Derived Vintana is Late Cretaceous, which means sisters to herbivorous marsupials were also present in the Mesozoic.
Figure 3. Mesozoic metatherians (in black), later taxa in gray. Whenever derived taxa are present in the Mesozoic (up to the Late Cretaceous) then ancestral taxa, or their sisters, were also present in the Mesozoic. Didelphis is extant, but probably unchanged since the Late Jurassic/Early Cretaceous.

Figure 3. Mesozoic metatherians (in black), later taxa in gray. Whenever derived taxa are present in the Mesozoic (up to the Late Cretaceous) then ancestral taxa, or their sisters, were also present in the Mesozoic. Didelphis is extant, but probably unchanged since the Late Jurassic/Early Cretaceous.

Mesozoic Eutherians (= Placentals)

  1. Rarely are placental mammals identified from the Mesozoic, because many are not considered placentals.
  2. Placentals (in the LRT) are remarkably rare in the Mesozoic, but sprinkled throughout the cladogram, such that all taxa more primitive than the most derived Mesozoic taxon (Anagale and derived members of the clade Glires, Fig. 4, at present a number of multituberculates) must have had Mesozoic sisters (Carnivora, Volitantia, basal Glires). 
Figure 4. Mesozoic euthrerians (placentals, in black). Later taxa in light gray. All taxa more primitive than Mesozoic taxa were likely also present in the Jurassic and Cretaceous. None appear after Onychodectes. Madagascar separated from Africa 165-135 mya, deep into the Cretaceous with a population of tenrecs attached. No rafting was necessary. 

Figure 4. Mesozoic euthrerians (placentals, in black). Later taxa in light gray. All taxa more primitive than Mesozoic taxa were likely also present in the Jurassic and Cretaceous. None appear after Onychodectes. Madagascar separated from Africa 165-135 mya, deep into the Cretaceous with a population of tenrecs attached. No rafting was necessary.

The above represents what a robust cladogram is capable of,
helping workers determine the likelihood of certain clades appearing in certain strata, before their discovery therein, based on their genesis, not their widest radiation or eventual reduction and extinction. In other words, we might expect sisters to basal primates, like adapids and lemurs, to be present in the Mesozoic, but not sisters to apes and hominids. We should expect sisters to all tree shrews and rodents to be recovered in Mesozoic strata. We should expect to see sisters to Caluromys, Vulpavus and other small arboreal therians/carnivorans in Mesozoic strata, but not cat, dog and bear sisters.

References
Smith T 2011. Contribution of Asia to the evolution and paleobiogeography of the earliest modern mammals. Bulletin des séances- Académie royale des sciences d’outre-mer. Meded. Zitt. K. Acad. Overzeese Wet.57: 293-305

The extant pika has a Late Jurassic sister: Henkelotherium

We’ve known
since 2016 that the tiny Late Jurassic mammal, Henkelotherium is a basal rabbit (contra traditional studies that exclude rabbits). Today the extant pika (genus: Ochotona, Figs. 1, 2) enters the large reptile tree (LRT, 1348 taxa).

Figure 1. Pika skull (genus: Ochotona) in three views.

Figure 1. Pika skull (genus: Ochotona) in three views. It’s cuter with a coat of fur (Fig. 2).

Figure 2. Pika is a basal rabbit that prefers mountainous terrain. A sister, Henkelotherium, goes back to the Late Jurassic.

Figure 2. Pika is a basal rabbit that prefers mountainous terrain. A sister, Henkelotherium, goes back to the Late Jurassic.

Ochotona princeps (originally Lepus dauuricus Pallas, 1776; Link 1795; Richardson 1828) is the extant pika, a rock-dwelling herbivore nesting between Henkelotherium and rabbits. Pikas live in mountainous areas in Asia and North America. Distinct from Henkelotherium, Ochotona is larger, with a near complete loss of the tail. Both have spreading metatarsals and four upper molars. In pikas the second incisors are posteromedial to the first incisors, creating a larger cheek area. A medial pedal digit 1 is present in both.

Fossil pikas are known from the Miocene, 16mya, to the recent, but Henkelotherium goes back to the Late Jurassic.

Figure 2. Henkelotherium reconstructed from DGS tracings in figure 1. Note the tiny manus and large pes, traits that continue into extant rabbits.

Figure 3. Henkelotherium reconstructed from DGS tracings in figure 1. Note the tiny manus and large pes, traits that continue into extant rabbits. The image is 75% larger than life size.

Figure 4. Subset of the LRT featuring Ochotona and the rabbits.

Figure 4. Subset of the LRT featuring Ochotona and the rabbits.

Henkelotherium guimarotae (Krebs 1991; Late Jurassic 150 mya, Fig. 3) was traditionally considered eupantothere. Henkelotherium nests within the rabbit clade as a very early member of the tree shrew/ shrew/ rodent/ rabbit clade: Glires. Like its sisters, the manus was small and the pes had long digits with sharp claws. The lumbar region was long and flexible, ideal for hopping and galloping. Note the long robust tail.

This new nesting further confirms
the hypothesis that rodents (including multituberculates) and rabbits (including Henkeleotherium) had a deep Mesozoic origin (Fig. 5).

Figure 1. Select basal cynodonts and mammals set chronologically. The divergence times for placentals (Eutheria), marsupials (Metatheria) and monotremes (Mammalia) are estimated here.

Figure 5. Select basal cynodonts and mammals set chronologically. The divergence times for placentals (Eutheria), marsupials (Metatheria) and monotremes (Mammalia) are estimated here.

References
Link HF 1795.  Über die Lebenskräfte in naturhistorischer Rücksicht und die Classification der Säugthiere. – Beyträge zur Naturgeschichte (Rostock, Leipzig) 2: 1-41.
Kear BP, Cooke BN, Archer M and Flannery TF 2007. Implications of a new species of the Oligo-Miocene kangaroo (Marsupialia: Macropodoidea) Nambaroo, from the Riversleigh World Heritage Area, Queensland, Australia, in Journal of Paleontology 81:1147-1167.
Krebs B 1991. Skelett von Henkelotherium guimarotae gen. et sp. nov. (Eupantotheria, Mammalia) aus dem Oberen Jura von Portugal. Berl Geowiss Abh A.: 133:1–110.

wiki/Pika
wiki/Henkelotherium

 

What is Rhamphocephalus? An earlier bird.

Some confusion in the academic literature today
as a Middle Jurassic fossil known since the 19th century is grossly misidentified.

Figure 2. Rhamphocephalus in situ, traced by Seeley, traced by O'Sullivan and Martill and Rhamphorhynchus graphic from Wellnhofer 1975.

Figure 1. Rhamphocephalus in situ, traced by Seeley, traced by O’Sullivan and Martill and, for comparison sake, Rhamphorhynchus graphic from Wellnhofer 1975, all appearing in O’Sullivan and Martill 2018. Rhamphocephalus has been traditionally identified as a pterosaur. That paradigm was challenged by O’Sullivan and Martill 2018, but that challenge is challenged again here.

Today a paper by O’Sullivan and Martill 2018
redescribes several fossils from the Middle Jurassic (165–166 mya) of England, traditionally ascribed to the wastebasket pterosaur taxon, Rhamphocephalus prestwichi (type, Seeley, 1880;  OUM J.28266; Figs. 1–4). Most of the disassociated specimens (individual jaws, limbs) are clearly pterosaurian. One (the goose-sized skull roof) is clearly not pterosaurian.

Figure 2. Rhamphorhynchus compared to a large choristodere, Simoedosaurus, and to a large thalattosuchian, Pelagosaurus. There is absolutely no match here.

Figure 2. O’Sullivan and Martill compared Rhamphocephalus to a large choristodere, Simoedosaurus, and to a large thalattosuchian, Pelagosaurus. There is absolutely no match here, either in size or morphology. Colors and ‘to scale’ Rhamphocephalus images added for clarity.

The holotype of Rhamphocephalus prestwichi,
“an isolated skull table, is found to be a misidentified crocodylomorph skull,” according to O’Sullivan and Martill, who illustrated the 10x smaller specimen alongside a dorsal view of the 3m long thalattosuchian (marine) croc, Pelagosaurus, from the Lower Jurassic of England and, perhaps to cover all their bases, flipped anterior-to-posterior alongside the Paleocene choristodere, Simoedosaurus (Fig. 2). Note: the authors did not illustrate their comparative taxa to scale (as shown above), perhaps because the taxa are 10x larger and are morphologically dissimilar. So why make such comparisons? I don’t understand the logic of these paleontologists making such readily disprovable comparisons.

Figure 1. The skull roof named Rhamphocephalus here with bones and teeth colored.

Figure 3. The in situ specimen of Rhamphocephalus here with bones and teeth colored. At standard monitor 72 dpi resolution, this image is 2x life size. Perhaps this skull can be µCT scanned for buried data. Some palatal elements are peeking out from the antorbital fenesrae and nares. The dentary teeth make a few appearances, too. This is a sharp-tipped taxon.

Traced here
using DGS methods (Fig. 3) and phylogenetically tested in the large reptile tree (LRT, 1321 taxa) goose-sized Rhamphocephalus nests with the hummingbird-sized, Hongshanornis (Fig. 2), an Early Cretaceous toothed bird from China. Hongshanornis is one of the few toothed birds in which the orbits are further forword, creating a longer cranium to match that of Rhamphocephalus. A suite of other skull traits are likewise most closely matched to Hongshanornis. The Rhamphocephlaus specimen appears to be complete without obvious breaks either at the toothy tip of the skull or the occiput. More teeth and bones were identified here.

Figure 2. Rhamphorcephalus in situ compared to Hongshanornis in situ to scale and enlarged to match.

Figure 2. Rhamphorcephalus in situ compared to Hongshanornis in situ to scale and enlarged to match skull length. To scale image (above) is 1.25x actual size, much too small for sea crocs. similar in size to pre-birds. Hongshanornis is a tiny bird, similar in size to a hummingbird.

Ironically
the authors report, “The earliest known record of Bathonian pterosaurs is an account of “fossil bird bones” from the Taynton Limestone Formation of Stonesfield by an anonymous author A.B., appearing in the March edition of the Gentleman’s Magazine of 1757.” For this specimen, and only this specimen, A.B. got it right. The other specimens are clearly pterosaurian.

Historically
the authors report, “This specimen is exposed on a limestone slab in dorsal view and was assigned to Pterosauria based on its perceived thin bone walls. Seeley (1880) noted that the arrangement of bones was more crocodilian than pterosaurian and considered this construction diagnostic of the new taxon. Significantly he (Seeley 1880: 30) stated: “I shall be quite prepared to find that all the ornithosaurians from Stonesfield belong to this or an allied genus which had Rhamphorhynchus for its nearest ally.” In the LRT crocodilians are closer to birds than pterosaurs are.

Figure 6. Rhamphocephalus chronologically precedes the Solnhofenbirds by several million years making it the oldest known bird.

Figure 6. Rhamphocephalus chronologically precedes the Solnhofenbirds by several million years making it the oldest known euornithine bird.

Is the Middle Jurassic too early for a toothed bird?
Perhaps not. Remembet that all of the Late Jurassic Solnhofen birds, traditionally named as one genus, Archaeopteryx, already represent a diverse radiation of taxa, suggesting an earlier genesis for that radiation. Rhamphocephalus indicates that the original bird radiation had its genesis at least 15 million years earlier. 

It is unfortunate
that O’Sullivan and Martill attempted to force fit the skull specimen into a crocodilian clade when no aspect of the thin-walled, goose-sized skull of Rhamphocephalus is crocodilian (Fig. 2)… or choristoderan (when flipped backwards!!). Adding Rhamphocephalus to the LRT gives it a single most parsimonious sister among all the toothed birds and a special Middle Jurassic place in the origin of birds story. All the details fit.

Working with a high-resolution image
of Rhamphocephalus (Fig. 3) copied from a PDF of the paper by O’Sullivan and Martill made this all possible.

Once again, to determine the affinities of a specimen it is more important to have a wide gamut of taxa to work with than to have firsthand access to the specimen itself. No one likes this method, but it clearly works time after time and to not use it invites discredit.

USE THE LRT. That’s what it is here for.

References
O’Sullivan M and Martill DM 2018. Pterosauria of the Great Oolite Group (Bathonian, Middle Jurassic) of Oxfordshire and Gloucestire. Acta Palaeontologica Polonica 63 (X): xxx–xxx, 2018 https://doi.org/10.4202/app.00490.2018
Seeley HG 1880. On Rhamphocephalus prestwichi Seeley, an Ornithosaurian from the Stonesfield Slate of Kineton. Quart. J. Geol. Soc. 36: 27-30.

wiki/Rhamphocephalus

Mammal taxa: origin times

A few days ago, we looked at a revised and expanded cladogram of the Mammalia based on skeletal traits (distinct from and contra to a cladogram based on DNA). Today we add chronology to the cladogram to indicate the first appearance of various mammals and estimate the origin of the various clades (Fig. 1).

Note that derived taxa
that chronologically precede more primitive taxa indicate that primitive taxa had their genesis and radiation earlier than the first appearance of fossil specimens, which always represent rare findings usually during wide radiations that increase the chance the specimen will fossilize in the past and be found in the present day.

Looking at time of mammal taxa origin categories:

Figure 1. Cladogram with time notes for the Mammalia (subset of the LRT).

Figure 1. Cladogram with time notes for the Mammalia (subset of the LRT).

Some notes:

  1. Both prototheres and basal therians were present (and probably widespread) in the Late Triassic.
  2. Derived prototheres appear in the Late Triassic, suggesting an earlier (Middle Triassic?) origin for Mammalia and an earlier (Middle Triassic?) split between Prototheria and Theria.
  3. Both fossorial metatherians and basal arboreal eutherians were present (and probably widespread) in the Late Jurassic. These were small taxa, out of the gaze of ruling dinosaurs.
  4. Large derived eutherians eolved immediately following the K-T boundary in the Paleocene and radiated throughout the Tertiary.
  5. A large fraction of prototherians, metatherians and eutherians are known only from extant taxa, some of which are rare and restricted, not widespread.
  6. Multituberculates and kin are derived placentals close to rodents by homology, not convergence.

 

Toxodon: now closer to kangaroos than to wombats

Figure 1. The skulls of Toxodon, Procoptodon and Interatherium resemble one another more than their post-crania might suggest. Now they nest together in the LRT (subset in figure 2).

Figure 1. The skulls of Toxodon, Procoptodon and Interatherium resemble one another more than their post-crania might suggest. Now they nest together in the LRT (subset in figure 2).

Another short one today
just to dash off a progress report as I wrestle with metatherian data. Like everyone else, I’m learning as I go. Toxodon and Eurygenium (Fig. 1) were always close to Interatherium, which was recently nested at the base of all kangaroos with the addition of the short-faced kangaroo, Procoptodon to the large reptile tree (LRT, 1258 taxa). Bulky, quadrupedal Toxodon and Eurgenium previously nested with quadrupedal wombats. 

The loss of pedal digit 1
found in kangaroos, interatheres and
Toxodon + Eurygenium turns out to be not a convergence, but a homoplasy as the Toxodon + Eurygenium node shifts over to the Interatherium node. All three are quadrupeds.

Now basal wombats with five pedal digits,
like the koala, no longer have four-toed taxa, like Eurygenium and Toxodon, separating them from their five-toed ancestors. 

Interatheres are getting to be more interesting. 

Figure 2. Subset of the large reptile tree focusing on the Metatheria. The tree is fully resolved, but many bootstrap scores under 50 indicate that only one or two characters separate those nodes with low scores. Scores higher than 50 are separated by three or more traits.

Figure 2. Subset of the large reptile tree focusing on the Metatheria. The tree is fully resolved, but many bootstrap scores under 50 indicate that only one or two characters separate those nodes with low scores. Scores higher than 50 are separated by three or more traits.

BTW
loss of pedal digit 1 also occurs alone in the wolf-like marsupial carnivore, the Tasmanian wolf, Thylacinus, by convergence.  By convergence, pedal digit 1 also shrinks in the bandicoot (Perameles) clade.

Geologically
western Gondwana (Africa + South America) separated from eastern Gondwana (Madagascar, India, Australia, Antartica) about 180 mya (Jurassic). That’s when the ancestors of South American Interatherium and Toxodon separated from the Australian ancestors of kangaroos. This is one way to estimate the antiquity of mammal clades.

Final thought for paleontologists and soon-to-be-paleontologists:
Reexamining data, like this, is good science. Making mistakes. like this, goes with the territory. Naiveté and enthusiasm go hand-in-hand. Apologies often follow. Gaining experience is a slog, but worthwhile when the puzzle pieces fit better in the end. More work often brings new insight. 

 

 

‘The Dawn of Mammals’ YouTube video illuminates systematic problems

Sorry, looks like video was yanked off of YouTube.

Part of this YouTube video (see below, click to view)
pits DNA paleontolgist, Dr. Olaf Bininda-Emonds (U. Oldenburg), against bone trait paleontologist, Dr. John Wible (Carnegie Museum of Natural History) in their common and contrasting search for basal placental mammals. Both realize that DNA cladograms do not replicate bone cladograms and DNA cannot be utilized with ancient fossils.

Dr. Bininda-Emonds, used molecular clocks
in living taxa to hypothetically split marsupials from placentals about 160 mya ago (Late Jurassic).

By contrast, Dr. Wible reports (28:53),
“Our study supported the traditional view that there were no fossils living during the Cretaceous [that] were members of the placental group itself. There were only ancestors of the placentals living.” (unscripted verbatim)

The impulse for this argument
came from the discovery of Maelestes (Wible et al. 2007a,b; 28:30 on the video) from the Late Cretaceous (75 mya). Dr. Wible’s paper nested Maelestes with the pre-placental, Asiorcytes, another tree-shrew-like mammal from the Late Cretaceous.

The large reptile tree
 (subset in Fig. 2) nests the first known placental mammals at the 160 mya mark, matching the DNA predictions of Dr. Bininda-Emonds et al. A long list of taxa, including Maelestes, nest in the Jurassic and Cretaceous, contra Wible et al. Only more complete taxa are tested in the LRT and dental traits are not emphasized.

Figure 2. Mesozoic time line showing the first appearances of several fossil mammals and the clades they belong to. Many, if not most of the listed taxa are late survivors of earlier radiations, sometimes much earlier radiations. Monodelphis and Didelphis are extant animals that originated in the Early Jurassic at the latest. Note also the large gaps over tens of millions of years, highlighting the rarity of fossil bearing locales.

Figure 2. Mesozoic time line showing the first appearances of several fossil mammals and the clades they belong to. Many, if not most of the listed taxa are late survivors of earlier radiations, sometimes much earlier radiations. Monodelphis and Didelphis are extant animals that originated in the Early Jurassic at the latest. Note also the large gaps over tens of millions of years, highlighting the rarity of fossil bearing locales.

In the video Dr. Wible says, “Many modern groups, according to the molecular clock analysis, actually are, they should be, present in the Cretaceous fossil record. We can’t find them.” Actually Dr. Wible already found them, but does not recognize them for what they are. That’s a common problem in paleontology, largely due to taxon exclusion, that we’ve seen before here, here, here and here. And in dozens of other mislabeled clades, like multituberculates.

The Bininda-Edmonds et al. paper reports,
“Here we construct, date and analyse a species-level phylogeny of nearly all extant Mammalia to bring a new perspective to this question. Our analyses of how extant lineages accumulated through time show that net per-lineage diversification rates barely changed across the Cretaceous/Tertiary boundary. Instead, these rates spiked significantly with the origins of the currently recognized placental superorders and orders approximately 93 million years ago, before falling and remaining low until accelerating again throughout the Eocene and Oligocene epochs. Our results show that the phylogenetic ‘fuses’ leading to the explosion of extant placental orders are not only very much longer than suspected previously, but also challenge the hypothesis that the end-Cretaceous mass extinction event had a major, direct influence on the diversification of today’s mammals.”

The LRT agrees with the timing indicated by the DNA analysis
Placentals are indeed found in the LRT Cretaceous and Jurassic fossil record (Fig. 2). They were not recognized by traditional workers using smaller taxon lists, for what they were. The LRT minimizes taxon exclusion and so solves many paleo problems with an unbiased and wide gamut approach currently unmatched in the paleo literature. Extant birds have a similar deep time record based on a few recent finds.

Perhaps overlooked
there are currently large gaps spanning tens of millions of years, highlighting the rarity of fossil bearing locales. All Mesozoic mammals are rare.

The DNA tree
of the Bininda-Emonds team correctly splits monotremes from therians, but incorrectly nests ‘Afrotherians‘ with Xenarthrans at the base of all mammals followed by moles + shrews, bats + carnivores + hoofed mammals + whales, followed by primates and rodents. As anyone can see, this is a very mixed up order, placing small arboreal taxa in derived positions and stiff-backed elephants and in in basal nodes. This DNA analysis is not validated by the LRT.

To its credit, basal mammals in the LRT
greatly resemble their marsupial ancestors. Then derived mammals become generally larger, with derived tooth patterns, stiffer dorsal/lumbar areas and longer pregnancies with more developed (precocious) young.

Given three cladograms of placental relationships,
none of them identical, how does one choose which one is more accurate? Here’s my suggestion: look at each sister at each node and see where you best find a gradual accumulation of derived traits, without exception. And look at outgroups leading to basal members of the in group.

Some readers are still having a hard time realizing
that someone without direct access to fossils and without a PhD is able to recover a more highly resolved cladogram that features gradual changes between every set of sister taxa than trees published over the last ten years in the academic literature. I agree. This should not be taking place. This is not what I expected to find when I started this 7-year project. One tends to trust authority. It’s been an eye-opening journey. In nearly all tested studies overlooking relevant taxa continues to be the number one shortcoming. The LRT minimizes that issue. The number two problem is blind faith in DNA results. The number three problem is an apparent refusal to examine phylogenetic results to weed out mismatched recovered sister taxa.

The video spends also some time with Zhangheotherium,
which we looked at earlier here and here. The interviewed workers talk about the ankle spur, but as a venom injector, as in the duckbill, Ornithorhynchus, not as a membrane frame, like a calcar bone, as in bats.

The video considers Repenomamus a large Early Cretaceous mammal
but the LRT nests Repenomamus as a late-surviving synapsid pre-mammal, derived from a sister to Pachygenelus, as we learned earlier here.

PS. As touched on earlier,
many basal arboreal mammals were experimenting with gliding (e.g. Volaticotherium and Maiopatagaium), but only one clade, bats, experimented with flapping. This was, perhaps not coincidentally, during the Middle to Late Jurassic (Oxordian, 160 mya). Remember, these gliding membranes were all extensions of the infant nursery membrane found in colugos and other volatantians, not far from the basalmost placental, Monodelphis.

References
Bininda-Emonds ORP, et al., (9 co-authors) 2007. The delayed rise of present-day mammals. Nature 446(7135):507-512.
Wible JR, Rougier GW, Novacel MJ and Asher RJ 2007a. The eutherian mammal Maelestes gobiensis from the Late Cretaceous of Mongolia and the phylogeny of Cretaceous Eutheria. Bulletin of the American Museum of Natural History 327:1–123.
Wible JR, Rougier GW, Novacek MJ and Asher RJ 2007b. Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary.” Nature, 447: 1003-1006.

Bird, pterosaur, dinosaur simplified chronology

Following the earlier post on non-arboreal post K-T boundary birds…

…this one pretty much speaks for itself.
Here (Fig. 1) is a chronology, very much simplified, of birds, pterosaurs and dinosaurs according to the LRT.

Figure 1. Mesozoic chronology of bird, dinosaur and pterosaur clades.

Figure 1. Mesozoic chronology of bird, dinosaur and pterosaur clades based on taxa in the LRT.

If you’re curious about any of the taxa,
in the chronology, simply use Keywords to locate them.