Yanoconodon: Proximal sister to the Mammalia

Updated September 22, 2018
with the addition of pertinent taxa.

This post was composed several weeks ago.
After all the intervening excitement I’m glad to bring Yanoconodon to your attention.

Yanoconodon alllini (Luo, Chen, Li and Chen 2007; Early Cretaceous, 122 mya; 13 cm in length; Figs. 1, 2) is known from a nearly complete and articulated crushed fossil. It is traditionally considered a eutriconodont, a clade that traditionally includes Spinoletes, Repenomamus, GobiconodonLiaoconodon and Jeholodens. Unfortunately that clade is paraphyletic in the large reptile tree (LRT) because other traditional members nest outside this clade in the LRT. Here Yanoconodon nests with Maotherium in that clade (Fig. 3).

Yanoconodon had a semi-sprawling posture
and a a long, robust torso with an unusually thick lumbar vertebrae provided with very short ribs. The limbs were short. The canines were quite narrow. The posterior jaw bones were still attached to the jaw. They had not yet become completely reduced to middle ear bones and completely separated from the jaw bones. So, by definition and cladogram (Fig. 3), Yanoconodon was not a true mammal. Wikipedia disagrees as that author reports, “Despite this feature Yanoconodon is a true mammal.”

FIgure 1. Yanaconodon nests as the proximal outgroup to the Mammalia in the LRT.

FIgure 1. Yanoconodon nests as the proximal outgroup to the Mammalia in the LRT. Even so it has several autapomorphies (differences from the actual  hypothetical ancestor.)

from the Luo, Chen and Chen abstract
“Detachment of the three tiny middle ear bones from the reptilian mandible is an important innovation of modern mammals. Here we describe a Mesozoic eutriconodont nested within crown mammals (1) that clearly illustrates this transition: the middle ear bones are connected to the mandible via an ossified Meckel’s cartilage. The connected ear and jaw structure is similar to the embryonic pattern in modern monotremes (egg-laying mammals) and placental mammals, but is a paedomorphic feature retained in the adult, unlike in monotreme and placental adults. This suggests that reversal to (or retention of) this premammalian ancestral condition is correlated with different developmental timing (heterochrony) in eutriconodonts. (2) This new eutriconodont adds to the evidence of homoplasy of vertebral characters in the thoraco-lumbar transition and unfused lumbar ribs among early mammals. (3) This is similar to the effect of homeobox gene patterning of vertebrae in modern mammals, making it plausible to extrapolate the effects of Hox gene patterning to account for homoplastic evolution of vertebral characters in early mammals.” (4)

Notes

  1. The LRT nests Yanoconodon just outside the crown mammals. Not sure why the authors say this, given what they report about the posterior jaw bones as posterior jaw bones.
  2. Curious that the retention of “this pre-mammalian ancestral condition” does not indicate to the authors that Yanoconodon is indeed a pre-mammal.
  3. Yanoconodon does not nest as an early mammal in the LRT.
  4. …or…not, if Yanoconodon is indeed a non-mammalian trithelodont. Other non-mammalian cynodonts lived alongside Jurassic mammals. Only one purported eutriconodont listed above is a mammal, Volaticotherium. It nests as a basal placental. Triconodon is a mammal, too, a monotreme known from just a dentary and teeth.
Figure 2. From Luo et al. the posterior jaw bones of Yanoconodon. These are not middle ear bones, so Yanoconodon is not a mammal.

Figure 2. From Luo et al. the posterior jaw bones of Yanoconodon. These are not middle ear bones, so Yanoconodon is not a mammal. The malleus is the articular. The incus is quadrate.

Yanoconodon is a great transitional fossil.
You can’t call it a mammal, because it nests outside the last common ancestor of all mammals.

Figure 3. Basal mammals begin with Ornithorynchus, the most primitive living mammal. Yanoconodon nests just outside this clade.

Figure 3. Basal mammals begin with Ornithorynchus, the most primitive living mammal. Yanoconodon nests just outside this clade.

References
Luo Z, Chen P, Li G, and Chen M 2007. A new eutriconodont mammal and evolutionary development in early mammals. Nature 446:15. online Nature

wiki/Yanoconodon

Romer’s ‘gap’ gets filled by Clack et al. 2016

According to Clack et al. 2016
“The term ‘Romer’s Gap’ was coined for a hiatus of approximately 25 million years (Myr) in the fossil record of tetrapods, from the end-Devonian to the mid-Mississippian (Viséan).”

This paper starts to fill Romer’s gap
with five new, incomplete taxa. three stem tetrapods and two stem amphibians, suggesting a deep split among crown tetrapods. That conclusion confirms an earlier one first reported here based on: (1) tetrapod footprints in the Middle Devonian, (2) the first appearance of reptiles in the Viséan and (3) the earlier split of microsaurs + amphibians, evidently before the end of the Devonian or at the very origin of the Carboniferouus following the post-Devonian extinction event.

Figure 1. Above, two trees recovered by Clack et al. 2016 compared to the one tree recovered by the LRT below.

Figure 1. Above, two trees recovered by Clack et al. 2016 compared to the one tree recovered by the LRT below. Left tree: Strict consensus of four equally parsimonious trees obtained from implied weights search with K = 4. Right tree:Bayesian analysis tree. Note the widely varying nesting sites of certain taxa.

Unfortunately the phylogenetic analyses
of Clack et al, (Fig. 1) fail to separate basal reptiles from microsaurs, fail to nest Gephyrostegus and Silvanerpeton as basalmost reptiles and fail to split basal reptiles into Archosauromorpha and Lepidosauromorpha in or before the Viséan. These problems are in addition to their inability to find accord in their own two published topologies (Fig. 1).

Figure 2. A new Romer's Gap taxon, Koilops, nests with basalmost tetrapods. The skull is similar to that of Acanthostega.

Figure 2. A new Romer’s Gap taxon, Koilops, nests with basalmost tetrapods. The skull is similar to that of Acanthostega. Note the interpretive changes between the the color version, which helps one understand the anatomy and the line art Clack et al. 2016 tracing, which still includes some guesswork and perhaps some misinterpretation. Large parts of the squamosal and postorbital are missing here. I’m not saying the colored tracing is 100% correct. This is a difficult fossil. I am saying it is so much easier to understand than the line drawing.

Koilops (Fig. 2) was a basal tetrapod, smaller than most.

Figure 2. Aytonerpeton is a tiny taxon with an inch-long skull. Here CT scans have helped delineate the bones colored for identification.

Figure 3. Aytonerpeton is a tiny taxon with an inch-long skull. Here CT scans have helped delineate the bones colored for identification. The orbit appears to have on odd bean shape, relatively large, but this is a tiny taxon.  CT scan from Clack et al. 2016.

Based on chronological and phylogenetic bracketing
we should expect to find amphibian-like reptiles (with amniote eggs) prior to the Viséan in Romer’s Gap, but they are likely to be a minority component. Utegenia, or similar sister, should be found there, along with other basal seymouriamorphs and reptilomorphs.

Figure 1. Which came first? The tracks or the trackmakers? In this case the tracks came first, strong indications that the variety of Devonian trackmakers we have found were all commonplace in the Late Devonian. The variety of basal reptiles and microsaurs found in the Visean must also reflect a wide radiation of derived taxa, pointing to an earlier origin.

Figure 4. From August 22, 2016, this graph shows what taxa are likely to be found in the late Devonian and Tournaisian (earliest Carboniferous = Romer’s Gap).

References
Clack JA and 14 other authors 2016. Phylogenetic and environmental context of a Tournaisian tetrapod fauna. Nature ecology & evolution 1, 0002 (2016) | DOI: 10.1038/s41559-016-0002

 

Fleshing out Andrewsarchus, the giant tenrec

Updated July 22, 2021
note that adding taxa moves Andrewsarchus and Rhynchocyon a node away from tenrecs.

All we know of Andrewsarchus
is its skull — without a mandible. A few days ago the dentary of a sister taxon, Sinonyx, was added to the skull of Andrewsarchus ((Osborn 1924; middle Eocene, 45 mya; AMNH 20135; 83cm skull length; also see Fig. 1) just to see if it would fit.

Before that…
everyone forever has always fleshed out Andrewsarchus like a giant bear/dog, moving the eyeballs to the top and giving it a bear/dog nose. Image googling Andrewsarchus will give you an idea what a widespread and accepted tradition that has been. I even followed that tradition back in 1989 in the book Giants, which you can see here as subset 1 of a larger pdf of the entire book.

Unfortunately,
Andrewsarchus does not nest with bears, dogs or mesonychids. It nests with tenrecs and Rhynchocyon (Fig. 2.), one type of elephant shrew. (The other type of elephant shrew is unrelated, as we learned here, Fig. 2). Tenrecs have a long flexible nose.

So, here, without further adieu
is a first shot at adding tenrec soft tissue to the skull of Andrewsarchus (Fig. 1). Is it close to being correct? I hope so, given the present evidence.

Figure 1. Andrewsarchus restored as giant tenrec alongside, Canis, the wolf to scale. Note the small and low-set eyes on Andrewsarchus. The mandible comes from Sinonyx. Note the natural tilt of the canid skull permitting binocular vision. Andrewsarchus had low-set eyes, rather un-canid-like. We have to give up the bear-dog restoration of Andrewsarchus.

Figure 1. Andrewsarchus restored as giant tenrec alongside, Canis, the wolf to scale. Note the small and low-set eyes on Andrewsarchus. The mandible comes from Sinonyx. Note the natural tilt of the canid skull permitting binocular vision. Andrewsarchus had low-set eyes, rather un-canid-like. We have to give up the bear-dog restoration of Andrewsarchus.

Now, just imagine the post-crania…
and the best clue we have is the living tenrec, Rhynchocyon (Fig. 2) with long legs, robust torso and short tail, only ten times bigger.

Figure 6. Rhynchocyon (above) and Macroscelides (below) compared. Though both are considered elephant shrews, they nest in separate major mammal clades in the LRT.

Figure 3. Rhynchocyon (above) and Macroscelides (below) the other type of elephant shrew compared. Though both are considered elephant shrews, they nest in separate major mammal clades in the LRT.

Maybe it’s time to 
give up the bear-dog restoration for Andrewsarchus and give it the giant  tenrec restoration it deserves based on phylogenetic bracketing and phylogenetic analysis.

Figure 3. The skull of Andrewsarchus mated to the body of Leptictis to make a chimaera.

Figure 3. The skull of Andrewsarchus mated to the body of Leptictis to make a chimaera.

References
Osborn HF 1924. Andrewsarchus, giant mesonychid of Mongolia. American Museum Noviattes 146: 1-5.

Pleuraspidotherium and Orthaspidotherium

These two taxa don’t make very many lists.
That may be because Pleuraspidotherium amonieri  (Paleocene; Lemoine 1882; Fig. 1) and Orthaspidotherium edwardsi (Ladevèze, Missiaen and Smith 2010; ) are not directly related to any ‘big name’ clades and they have a very basal condylarth (herbivorous mammal) look. Instead these two nest with rather plesiomorphic Meniscotherium and highly derived Astrapotherium in the large reptile tree (LRT, 898 taxa). Both Pleuraspidotherium and Orthaspidotherium were originally recognized as phenacodontids related to Meniscotherium, so we’re tracking traditional nestings here.

Figure 1. Orthaspidotherium from x et al. 2009 is a plesiomorphic mammalian herbivore, basal to all later forms, from elephants to baleen whales to giraffes.

Figure 1. Orthaspidotherium from Ladevèze, Missiaen and Smith 2010 is a plesiomorphic mammalian herbivore, basal to all later forms, from elephants to baleen whales to giraffes.

However in the LRT,
both taxa nest together and apart from Phenacodus.

Figure 1. Pleurospidotherium a

Figure 1. Pleuraspidotherium a

These two were among the very first
slightly larger mammalian herbivores that first appeared in the Cenozoic. We see the origin of the notched diastema here separating the anterior premolars from the poster premolars and molars.

Figure 2. Subset of the LRT showing the nestings of Pleurospidotherium and Orthaspidotherium at the base of the herbivorous mammals.

Figure 2. Subset of the LRT showing the nestings of Pleurospidotherium and Orthaspidotherium at the base of the herbivorous mammals.

Halliday 2015 reports
“Ladevéze et al. (2010) hypothesised that Pleuraspidotheriidae are closest relatives to arctocyonids such as Chriacus, in a group also including the basal artiodactyls, but their taxonomic sampling was very low, and only very few representatives of each supposed group were present.” 

In the LRT
Chriacus nests with bats and Arctocyon nests with Didelphis in the Metatheria, both far from the Pleuraspidotheriidae. None of these relationships is found in Halliday et al. 2015.

Halliday 2015 reports, 
“With the exception of Primates (Russell, 1964), Rodentia (Jepsen, 1937), and Carnivora (Fox, Scott & Rankin, 2010), no extant order of placental mammal has an unambiguous representative during the Paleocene.” Pleuraspidotherium and Orthaspidotherium are also in the Paleocene, so they are early representatives of the herbivorous placental clades.

“Despite numerous suggestions of Cretaceous placentals, no Cretaceous eutherian mammal has been unambiguously resolved within the placental crown.” In the LRT multituberculates and Shenshou from the Jurassic are rodent sisters, Volaticotherium is a basal pre-placental from the earliest Cretaceous. Docofossor is a basal Oxfordian (early Late Jurassic) marsupial.  Maotherium a pre-mammal from the early Cretaceous, Zhangheotherium, a basal pangolin is from the earliest Cretaceous, and Maelestes, a basal tenrec is from the late Cretaceous, so the Halliday claim is not validated by the LRT and a Cretaceous origin would therefore NOT require the existence of long ghost lineages, contra Halliday et al. 2015.

Halliday et al. 2015 illustrates
the ‘current consensus” of mammalian relationships with the first split at Xenarthra + Tenrecoidea and kin splitting from Glires + the rest of the placentals in something of a mishmash of tree branches. The LRT, by contrast, recovers complete resolution at all branches and does not replicate the “consensus” topology.

Halliday et al. then reports on their own phylogenetic analysis based on 680 traits and 177 taxa. The resulting topology bears little similarity to the the LRT with the first split separating (primates + plesiadapids) + (rodents + rabbits) + xenarthra  from the rest of the placentals, then Phenacodus + Meniscotherium and kin splitting next from the remaining placentals in one test.

Another result split Xenarthra and Procavia + Potamogale and kin from the rest of the mammals. Among their seven conclusions, they report, “No definitive crown-placental mammal has yet been found from the Cretaceous, as Protungulatum is resolved as a stem eutherian, and therefore the Cretaceous occurrence of Protungulatum cannot be considered definitive proof of a Cretaceous origin for placental mammals.”

This is contradicted by the LRT results.

References
Halliday T et al. 2015. Resolving the relationships of Paleocene placental mammals. Biologoical Reviews. doi: 10.1111/brv.12242
Ladevèze S, Missiaen P and Smith T 2010. First Skull Of Orthaspidotherium edwardsi (Mammalia, “Condylarthra”) From The Late Paleocene Of Berru (France) And Phylogenetic Affinities Of The Enigmatic European Family Pleuraspidotheriidae”. Journal of Vertebrate Paleontology. 30 (5): 1559–1578.
Lemoine V 1882. Sure l’encephale de l’Artocyon et du Pleurospidotherium aumonieri. Bulletin de la Societe Géologie de France 3 series t. X. Also. Comptes Rendus.

wiki/Orthaspidotherium
wiki/Pleuraspidotherium 

An imaginary mandible for Andrewsarchus

All I did
was take the mandible from sister Sinonyx and scale it to Andrewsarchus (Fig. 1; Osborn 1924). I also added a patch to extend the apparently broken and missing posterior nasals over the fontanelle between the frontals because that’s how far the nasal extends in Sinonyx.

See how sometimes
you don’t ‘see’ something until after you see it in a sister?

Figure 1. Andrewsarchus with Sinonyx mandible. The lower canine helps constrain the shape of the missing upper canine. 

Figure 1. Andrewsarchus with Sinonyx mandible. The lower canine helps constrain the shape of the missing upper canine. Note the transparent extension of the posterior nasals to cover up the fontanelle between the frontals, as in Sinonyx.

BTW
it bothered me that Sinonyx and Andrewsarchus were so much larger than their sisters, especially their closest sister, a type of elephant shrew, Rhynchocyon. Moreover, several traits appear to be homologous. So I retested the relationship of Sinonyx and Andrewsarchus with mesonychids and I retested them with prejudice. Any traits that could relate Sinonyx and Andrewsarchus with mesonychids I scored that way.

In the end,
I was not able to nest Sinonyx and Andrewsarchus with mesonychids.

Furthermore
when I removed all tenrec and odontocete sisters from the tenrec clade (see Fig. 2), leaving only Sinonyx and Andrewsarchus alone they still did not nest with mesonychids, but kept their node unchanged between the Ptilocercus clade and Onychodectes.

Figure 3. Tenrec-Odontocete clade with Leptictis now nesting with the elephant shrew Rhynchcyon and the long-tailed tenrecs nesting with the short tailed tenrecs, basal to Pakicetus.

Figure 2. Tenrec-Odontocete clade with Leptictis now nesting with the elephant shrew Rhynchcyon and the long-tailed tenrecs nesting with the short tailed tenrecs, basal to Pakicetus. This tree moves Sinonyx closer to Pakicetus. Indohyus has already been associated with pakicetids.

Testing like this
brought certain problems to the surface. The current tree has been improved over earlier versions.

Here’s how the tenrec clade now stands:
(Fig. 2) Leptictis and the elephant shrew Rhynchocyon now nest together. They are both similar in size and build.

Giant Andrewsarchus and smaller Sinonyx still nest together. Would still like to see some post-crania for  these two.

The two living short-tailed terrestrial tenrecs, Hemicentetes and Tenrec now nest with two extinct long-tailed aquatic tenrecs, Lepticitidium and Indohyus. The latter has already been associated with pakicetids in the literature  (Rao 1971, Thewissen et al. 2007.)

Likewise Sinonyx and Andrewsarchus have already been associated with the origin of whales in the literature. The new tree topology brings them closer to Pakicetus.

Early members of the tenrec clade
were insectivore speedsters with long slender legs, based on the habits of Rhynchocyon. More derived tenrecs like Tenrec, are not speedy and Hemicentetes is protected with spinesLeptictidium had much longer hind limbs than fore limbs and was likely bipedal. Indohyus had subequal limbs so likely remained a quadruped. Tradtionally Indohyus has been considered an artiodactyl, but given the opportunity to nest with artiodactyls in the LRT, it does not do so.

Perhaps the most convergent clade
By all the present evidence, some tenrecs converged with rabbits and elephant shrews, some with mesonychids, others with artiodactyls and still others with mysticete whales. It’s a pretty amazing and woefully under appreciated clade.

It is interesting to consider the possibility
that since both elephant shrews and tenrecs have a proboscis that extends beyond the jaw line, it is possible that early land whales, Andrewsarchus and Sinonyx, might have had a similar long nose. Some of these taxa might have used such a snorkel to breathe while underwater, just below the surface — or — the long nose was the first soft tissue to disappear during the transition, because whales have no such nose.

References
Osborn HF 1924. Andrewsarchus, giant mesonychid of Mongolia. American Museum Noviattes 146: 1-5.
Rao AR 1971. 
New mammals from Murree (Kalakot Zone) of the Himalayan foot hills near Kalakot, Jammu and Kashmir state, India. Journal of the Geological Society of India. 12 (2): 124–34.
Thewissen JGM, Cooper LN, Clementz MT, Bajpai S and Tiwari BN 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature 450:1190-1195.

wiki/Leptictidium
wiki/Indohyus

 

 

Pigs and whales? No.

Sometimes when you add a common extant taxon
to the LRT, there can be more here than meets the eye. That was the case with Sus, the extant pig (Fig. 1).

Figure 1. Skeleton of Sus, the pig, a taxon commonly used as an outgroup for whales. In the LRT it is a sister to other even-toed ungulates, like Giraffa, not Odontoceti nor Mysticeti.

Figure 1. Skeleton of Sus, the pig, a taxon commonly used as an outgroup for whales. In the LRT it is a sister to other even-toed ungulates, like Giraffa, not Odontoceti nor Mysticeti.

Backstory
I was looking at a list of outgroup taxa for whales in Bianucci and Gingerich 2011 and comparing to to the outgroup taxa for whales in Geisler et al. 2011 and other workers:

  1. Gingerich 2011 listed: Elomeryx and illustrated a cow (Bos).
  2. Bianucci and Gingerich 2011 listed: Sinonyx, Mesonyx, Hippopotamus and Sus in that order toward Cetacea.
  3. Geisler et al. listed: Sus, Bos and Hippopotamidae in that order toward Cetacea.
  4. O’Leary and Gatesy 2008 listed: Eoconodon, Sinonyx and Hapalodectes [all considered Mesonychia by them]
  5. O’Leary et al. 2013 listed: Sus, Bos and Hippopotamus in that order toward Cetacea.

Note that
Sus, the pig; Bos, the cow; and Hippopotamus, the obvious, somehow makes it to three lists as outgroup taxa for whales in general. Believe it or not, these three earned their status after testing by traditional paleontologists. Despite having very few traits in common with whales, creating a great leap of phylogenetic faith to connect them all. If you’re bothered by that, I join you!

Figure 1. Ancodus nests as a more derived sister to Sus and it retains digit 1 on the manus and pes.

Figure 2. Ancodus nests as a more derived sister to Sus and it retains digit 1 on the manus and pes. Is this the same taxon as Elomeryx? If not, they appear to be quite close.

Sidenote:
Elomeryx (see above) is said to be widespread and common, but apparently has been confused online with Ancodus (Fig. 1). Are they the same? If different, how different? I’m confused and could use some clarity.

When we add Sus to the LRT
Sus nests much more reasonably between Tapirus and Ancodus (Fig. 2), two pig-like taxa with hooves. Notably extant Sus (Fig. 2) loses digit 1 on both the manus and pes while extinct Ancodus retains those digits indicating a convergent loss of these digits in the ancestors of pigs and in the ancestors of deer + giraffes.

By contrast O’Leary and Gatesy 2008 report, 
“Cetacea was the extant sister taxon of Hippopotamidae, followed successively by Ruminantia, Suina and Camelidae. The wholly extinct Mesonychia was more closely related to Cetacea than was any ‘‘artiodactylan. The osteological–dental data alone, however, did not support inclusion of cetaceans within crown ‘‘Artiodactyla.’ Recently discovered ankle bones from fossil whales reinforced the monophyly of Cetartiodactyla but provided no particular evidence of derived similarities between hippopotamids and fossil cetaceans that were not shared with other ‘‘artiodactylans’’. Can you sense their lack of resolution? Based on present evidence, O’Leary and Gatesy were suffering from taxon exclusion.

No such problem
with the LRT where whales are not related to pigs, cows or camels. Odontocete whales arise from tenrecs. Mysticete whales arise from desmostylians, as we learned earlier here.

References
Bianucci G and Gingerich PD 2011. Aegyptocetus tarfa, n. gen. et sp. (Mammalia, Cetacea), from the middle Eocene of Egypt: clinorhynchy, olfaction, and hearing in a protocetid whale. Journal of Vertebrate Paleontology. 31 (6): 1173–88.
Demere TA, McGowen MR, Berta A & Gatesy J. 2008.
 Morphological and Molecular Evidence for a Stepwise Evolutionary Transition from Teeth to Baleen in Mysticete Whales, Systematic Biology, 57 (1) 15-37. DOI: 10.1080/10635150701884632\
Geisler JH, McGowen MR, Yang G and Gatesy J 2011. A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea. Evolutionary Biology 11:112.
Gingerich PD 2005. Aquatic Adaptation and Swimming Mode Inferred from Skeletal Proportions in the Miocene Desmostylian Desmostylus. Journal of Mammalian Evolution, Vol. 12, Nos. 1/2, June 2005.
Gingerich PD 2011. Evolution of whales from land to sea. online here.
Marx FG and Fordyce RE 2015. Baleen boom and bust: a synthesis of mysticete phylogeny, diversity and disparity, Royal Society open Science 2:14034.
Marx FG, Hocking DP, Park T, Ziegler T, Evans AR and Fitzgerald EMG 2016. Suction feeding preceded filtering in baleen whale evolution. Memoirs of Museum Victoria 75:71-82.
O’Leary et al. 2013 The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals. Science 339. 662 SuppData.
O’Leary MA and Gatesy J 2008. Impact of increased character sampling on the phylogeny of Cetartiodactyla (Mammalia): combined analysis including fossils. Cladistics 24:397-442.

 

A Dinosaur Year 1989 Calendar

This ‘blast from the past’ by request: 
Click here or on image to download all 13 lorez images from my 1989 Dinosaur Year calendar, published by Alfred A. Knopf, New York. Thanks for the request, Leo!

I see two copies are presently available from Amazon.com here.

Click to download PDF of cover + 12 months of 1989 Dinosaur Year Calendar pix by David Peters at 72 dpi. It's over 25 years old and you'll find mistakes here. It was a product of its time.

Click to download PDF of cover + 12 months of 1989 Dinosaur Year Calendar pix by David Peters at 72 dpi. It’s over 25 years old and you’ll find mistakes here. It was a product of its time.

The calendar is over 25 years old
and you’ll find mistakes galore. It was a product of its time and the first time I ever painted dinosaurs in settings.

This followed
the book GIANTS and A Gallery of Dinosaurs, which illustrated dinosaurs on white backgrounds, all to the same scale. Both books are available as pdf files here and as used books at several online sites.

Where are the originals?
Collectors purchased all the originals except for the Brachiosaurus family in a pond (December) because it has a razor knife cut in the sky over the mountain top, inflicted upon opening the package at the publisher. It’s hanging on the wall over my monitor as I type this and I never notice the slit.

But wait! There’s more!
Click here to connect to a FREE build-it-yourself paper Pteranodon model.
And click here to connect to a FREE build-it-yourself paper Thalassomedon model.
All you need is 8.5×11″ bristol (stiff) paper, some glue or tape and a scissors or knife. Have fun, kids!

What is Darwinius?

Franzen et al. 2009
reported on a well-preserved small primate from 50mya named Darwinius.

From the Franzen et al. 2009 conclusion:
“Darwinius masillae represents the most complete fossil primate ever found, including both skeleton, soft body outline and contents of the digestive tract. Study of all these features allows a fairly complete reconstruction of life history, locomotion, and diet. Any future study of Eocene-Oligocene primates should benefit from information preserved in the Darwinius holotype. Of particular importance to phylogenetic studies, the absence of a toilet claw and a toothcomb demonstrates that Darwinius masillae is not simply a fossil lemur, but part of a larger group of primates, Adapoidea, representative of the early haplorhine diversification.”

In a published comment Beard 2009 wrote:
“Unbridled hoopla attended the unveiling of a 47-million-year-old fossil primate skeleton at the American Museum of Natural History in New York on 19 May. Found by private collectors in 1983 in Messel, Germany, the press immediately hailed the specimen as a “missing link” and even the “eighth wonder of the world.”

“Overall proportions and anatomy resemble that of a lemur, and the same is true for other adapiform primates. A new genus and species of adapiform primate, Darwinius masillae (Franzen et al., 2009; Eocene, 50 mya ). The adapids are a branch of the primate tree that leads to modern lemurs. Ida would have to have anthropoid-like features that evolved after anthropoids split away from lemurs and other early primates. Here, alas, Ida fails miserably.” The reasons for that “fail” were not listed in the Beard note.

Taxon exclusion?
The large reptile tree, (LRT, 896 taxa), currently tests only a few primates. At this stage, Darwinius does indeed nest at the base of higher primates (simians), alongside Tarsius, the extant tarsier, but there are many dozen primate taxa that have not been included in the LRT.

Figure 1. Darwinius overall plus an X-ray showing the transition from milk teeth to adult teeth in this juvenile specimen.

Figure 1. Darwinius overall plus an X-ray showing the transition from milk teeth to adult teeth in this juvenile specimen.

In the LRT,
nesting only a few primates at present, the adapid prosimian, Notharctus, is basal to higher primates including humans (genus Homo). Tarsius, the tarsier, nests between Notharctus and Proconsul, a basal anthropoid (ape). Darwinius nests with Tarsius, but lacks the many specialized autapomorphies that characterize extant tarsiers like:

  1. oversized eyes
  2. distally fused tibiafibula
  3. elongated pedal digits 4 and 5.
  4. hyperelongated astragalus and calcaneum
  5. cervicals insert further beneath the skull
Figure 2. Tarsius, the extant tarsier. Note the several autapomorphies displayed here vs. the many plesiamorphies in Darwinius.

Figure 2. Tarsius, the extant tarsier. Note the several autapomorphies displayed here vs. the many plesiamorphies in Darwinius.

Wikipedia reports
“Most experts hold that the higher primates (simians) evolved from Tarsiidae, branching off the Strepsirrhini before the appearance of the Adapiformes.” If true, Darwinius is close to the lineage of humans. “A smaller group agrees with Franzen et al. that the higher primates descend from Adapiformes (Adapoidea). The view of paleontologist Tim White is that Darwinius is unlikely to end the argument.” 

NBC news reports,
here that “Ida is as far removed from the monkey-ape-human ancestry as a primate could be, says Erik Seiffert of Stony Brook University in New York. The new analysis says Darwinius does not belong in the same primate category as monkeys, apes and humans. Instead, the analysis concluded, it falls into the other major grouping, which includes lemurs.”

Nature reports on the “media frenzy”
here in a paper entitled: A hyped-up fossil find highlights the potential dangers of publicity machines.  To be fair, the authors’ claims at the press conference were appropriately measured. Nonetheless, the researchers were fully involved in the documentaries and the media campaign, which associate them with a drastic misrepresentation of their research.”

“Another damaging aspect of the events was the unavailability of the paper ahead of the press conference and initial media coverage. This prevented scientists other than those in the team from assessing the work and thereby ensuring that journalists could give a balanced account of the research.

“There is no reason to think that PLoS ONE’s editors and reviewers did less than their duty to the paper. Nonetheless, the clock was ticking at the time of submission.”

“In principle, there is no reason why science should not be accompanied by highly proactive publicity machines. But in practice, such arrangements introduce conflicting incentives that can all too easily undermine the process of the assessment and communication of science.”

The primate experts can hash this out.
At present, with so few primates tested, Darwinius is still a candidate to be at the transition from prosimian to simian in the LRT, as it presently nests… until additional taxa knock it out.

Added within minutes of posting
I ran across this reference:
Gingerich PD et al. 2010. Darwinius masillae is a Haplorhine — Reply to  Williams et al. (2010). Journal of Human Evolution. 59(5)574-576 where they report, “Williams et al. (2010) imply that ‘total evidence’ means study of hundreds of characters in a great many taxa. However, total evidence is about combining data before analysis and not about the size of the resulting matrix. “We agree with Seiffert et al., 2009 and Williams et al., 2010, and others that there is a strepsirrhine–haplorhine dichotomy in primate evolution. We employ the same cladistic methods. We accept that total evidence drawn from many sources is advantageous. Why then do we reach such a different conclusion about the systematic position of Darwinius? Given that our methods are the same, then our contrasting results can only be explained by differences in the number and balance of taxa chosen for study, the character matrix used to analyze higher-level primate phylogeny, the outgroup chosen to root a phylogenetic network, or some combination of these.”
More details on their arguments are found here.

References
Beard C 2009. Why Ida is fossil is not the missing link. Comment, NewScientist.
Online here.
Franzen JL, Gingerich PD, Habersetzer J, Hurum JH, Von Koenigswald W and Smith BH 2009. Complete primate skeleton from the Middle Eocene of Messel in Germany: morphology and paleobiology PLoS ONE. 4 (5): e5723.

wiki/Darwinius

nature.com article that touches on Darwinius

 

Baleen boom and bust

A year and a half ago
Marx and Fordyce 2015 entitled an academic paper on whale evolution, “Baleen boom and bust.” The authors report, “The phylogeny of 90 modern and dated fossil species suggests three major phases in baleen whale history: an early adaptive radiation (36–30 Ma), a shift towards bulk filter-feeding (30–23 Ma) and a climate-driven diversity loss around 3 Ma.”

As part of their introduction,
Marx and Fordyce report, “Past studies have fundamentally disagreed on the phylogenetic position, and even monophyly, of many extant and extinct taxa, with major implications for tree topology and molecular estimates of divergence times. Such problems probably reflect limited taxonomic sampling, which is known to compromise both phylogenetic accuracy  and macroevolutionary inferences. Another key problem is the presentation of morphological data as simple character-based scorings, which are usually unsupported by illustrations and hence difficult to comprehend or repeat.”

That’s what I keep saying,
although I’m new to mysticetes. To their credit Marx and Fordyce score 90 taxa for 37,000+ molecular and 272 morphological characters. The project is illustrated with 400 annotated specimens at morphobank.org: project 687. Their oldest taxon is Himalaycetus (Bajpai and Gingerich 1998) from the early Eocene (53.5mya), so this stacks up to be an excellent paper…

except for a few things…

First a little backstory on Himalayacetus
The specimen is the central portion of a left dentary with molar teeth. In vivo the dentqry would have been about 30 cm long, so in the range of Pakicetus. Baipai and Gingerich compared Himalayacetus to Sinonyx, which they considered a mesonychid, and a “representative middle Eocene archaeocete.” In the LRT, you might remember, Sinonyx nested with tenrecs, not mesonychids. Based on chemical analysis, Himalayacetus frequented fresh and salt water, but was found in marine strata.

And here’s where Marx and Fordyce made their mistake(s).
Rather than testing a wide gamut of mammals as potential whale ancestors, Bajpai and Gingerich settled on tradition as they wrote, “Following Van Valen (1966), archaeocetes are generally regarded as descendants of Mesonychia, with which they were long confused.”

As readers all know by now,
“generally regarded” doesn’t cut the mustard anymore, not when testing will tell you what is… and what is not. The LRT shows that mesonychids are distant relatives of mysticetes. Hippos and desmostylians, like Behemotops, are much closer. Desmostylians have been overlooked by whale workers. And Sinonyx is not a mesonychid. It nests with tenrecs, including some giant ones like Andrewsarchus, even when given the opportunity to nest with mesonychids and hippos, which likewise do not nest with artiodactyls in the LRT.

Bajpai and Gingerich report, “The time of divergence of extant Cetacea from extant Artiodactyla is unchanged and lies in the range of 62.5–66.4 Ma, at or near the beginning of the Cenozoic.” Then they report, “Some systematists using molecular genetic clocks suggest divergence of Cetacea from other orders of mammals in the Mesozoic as early as 100 Ma, but the quantified likelihood of such a hypothesis is vanishingly small from the point of view of known fossils and radiometric calibration of the geologic time scale.”

In other words,
they took data and verbally diminished its importance before scientific testing. They assumed that whales are monophyletic. It’s really not their fault. The hypothesis of a separation of odontocetes from mysticetes is only a few weeks old and they published about 70 weeks ago and were no doubt writing their manuscript months to years before that.

So to sum up, except for the invalidated relationship
between basal mysticetes and basal odontocetes, the interrelationships between most of the whale taxa in Marx and Fordyce are valid —

…with a second exception that
some toothed whales are, but should not be, in the lineage of mysticetes…

…with a third exception that
primitive gray whales (Eschritus robustus) nest as highly derived in Marx and Fordyce, while highly derived right whales (Eubalaena australis) nest closer to the origin of baleen whales. So the phylogenetic order of those mysticetes is reversed…

…with a fourth exception that
Janjucetus is considered a basal mysticete and it is not that closely related. It nests with Anthracobune in the LRT and, since that clade is more primitive than the Desmostylia, Janjucetus probably had legs.

That these workers 
accepted the “generally regarded” ancestors without testing is something that can be repaired. All they have to do is add the intervening taxa listed by the LRT to their analysis. When that happens, Janjucetus will nest with Anthracobune. Baleen whales will be derived from desmostylians. Gray whales will nest primitively. Odontocete whales will nest with a long line of extinct and extant tenrecs. And all the currently known fossil toothed whales with nest with odontocetes.

All of these arguments also apply to 
Geisler et al. 2011, who used Sus (pig), Bos (cattle) and Hippopotamus as outgroups with a basal split between mysticetes and odontocetes. Of course there is a HUGE morphological gap between hippos and whales that is conveniently overlooked everywhere but in the LRT.

Which brings up the Yamatocetus illustration problem.
Yamatocetus (Fig. 1, lower left) is a cetiothere mysticete, but Marx et al. 2016 illustrated their Yamatocetus with tiny teeth that don’t appear to be present in photos of the specimen. You can see those photos here: morphobank.org: project 687. Moreover, teeth or not, Yamatocetus nests in the LRT after several toothless taxa. Flat straight jaws in mysticetes is a derived trait, which I can see could be confusing if you are in the monophyletic whales camp. Moreover, considering the extreme flatness of the Yamatocetus rostrum with rather sharp edges, if even rudimentary teeth were present they should, like all marginal teeth, erupt from the jaw margins. If oriented toward the dentary there is little to no room for tooth roots. In short, I think the illustrated teeth are dubious. Send me datum to the contrary if you have it.

Also note
the rather substantial morphological leap from the unnamed NMV P2525677 suction feeding odotocete (Fig. 1, upper right) to passively filtering mysticete Yamatocetus, (Fig. 1, lower left). Odontocetes are active hunters, as were their tenrec ancestors. Mysticetes are passive grazers, as were their desmostylian ancestors.

The origin of baleen
still appears to belong to derived desmostylians (Fig. 3), with concave ventral rostral margins, as noted earlier here and preserved in basal mysticetes.

Figure 2. from Marx et al. 2016. presumes the monophyly of whales and the origin of mysticetes from odontocetes with small teeth. Both are not supported by the LRT. Upper left: Dorudon. Upper right: NMV P2525677. Lower left: Yamatocetus Lower right: Eschrichtius.

Figure 2. from Marx et al. 2016. presumes the monophyly of whales and the origin of mysticetes from odontocetes with small teeth. Both are not supported by the LRT. Upper left: Dorudon. Upper right: NMV P2525677. Lower left: Yamatocetus Lower right: Eschrichtius. When desmostylians are added, Eschrichtius becomes the basalmost mysticete and Yamatocetus is derived.  Were teeth present in Yamatocetus? I have yet to see evidence for teeth, which should be absent in such a derived taxon. I have not seen photos of the Yamatocetus mandible. Does it exist?

Before leaving this topic
the convergence of mysticetes with odontocetes is truly so remarkable that it has gone unnoticed for all this time by both professionals and amateurs alike. To those who dismiss the ability of the LRT to lump and separate such closely convergent taxa, this has been a test of that ability.

Figure 1. Paleoparadoxia. Note the gap left by the diastema between the anterior and posterior teeth. With the phylogenetic placement of desmostylians at the base of the Mysticeti, can this gap be where baleen (light blue) originated? Good question.. The loss of teeth and the elaboration of the baleen in transitional taxa would take us to the toothless, baleen endowed whales.

Figure 3. Paleoparadoxia. Note the gap left by the diastema between the anterior and posterior teeth. With the phylogenetic placement of desmostylians at the base of the Mysticeti, can this gap be where baleen (light blue) originated? Good question.. The loss of teeth and the elaboration of the baleen in transitional taxa would take us to the toothless, baleen endowed whales. Note the similarity of Eschrichtius (Fig. 1, lower right).

References
Demere TA, McGowen MR, Berta A & Gatesy J. 2008. Morphological and Molecular Evidence for a Stepwise Evolutionary Transition from Teeth to Baleen in Mysticete Whales, Systematic Biology, 57 (1) 15-37. DOI: 10.1080/10635150701884632\
Geisler JH, McGowen MR, Yang G and Gatesy J 2011. A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea. Evolutionary Biology 11:112.
Gingerich PD 2005. Aquatic Adaptation and Swimming Mode Inferred from Skeletal Proportions in the Miocene Desmostylian Desmostylus. Journal of Mammalian Evolution, Vol. 12, Nos. 1/2, June 2005.
Marx FG and Fordyce RE 2015. Baleen boom and bust: a synthesis of mysticete phylogeny, diversity and disparity, Royal Society open Science 2:14034.
Marx FG, Hocking DP, Park T, Ziegler T, Evans AR and Fitzgerald EMG 2016. Suction feeding preceded filtering in baleen whale evolution. Memoirs of Museum Victoria 75:71-82.
Okazaki Y 2012. A new mysticete form the upper Oligocene Ashiya Group, Kyushu, Japan and its significance to mysticete evolution. Bulletin of the Kitakyushu Museum of Natural History and Human History Series A (Natural History) 10:129-152.
Shikama T 1966. Postcranial skeletons of Japanese Desmostylia. Palaeontol. Soc. Japan Spec. Pap. 12: 1–202.

 

 

Further evidence for digitigrady in the multituberculate Kryptobaatar

Earlier we looked at
PILs, parallel interphalangeal lines (Peters 2000, 2010), which appear in a wide variety of tetrapod extremities, typically, but not always, aligning phalanges in parallel sets. Note the PILs of the plantigrade pes of Kryptobaatar (from Kielan-Jaworowska and Gambaryan 1994; Fig. 1 left) become better aligned when the pes is elevated to the digitigrade configuration (Fig. 1 right), as illustrated by Kielan-Jaworowska and Gambaryan in their 1994 paper (Fig. 1 middle).

note the PILs of Kryptobaatar become better aligned when the pes is elevated to the digitigrade configuration.

note the PILs of Kryptobaatar become better aligned when the pes is elevated to the digitigrade configuration. Note the angled calcaneum and reduced astragalus, two derived traits.

Living taxa that are both digitigrade and arboreal
include the big cats. The claws are not so sharp and not so curved, but they are long and their keratin sheath may have been much sharper and more curved.

Note the very short astragalus
and the calcaneum positioned at an odd lateral angle. These unique traits suggested to early researchers that Kryptobataar could have rotated its ankle to a great degree, ideal for establishing a good grip from any angle, even inverted, on a tree limb.

References
Kielan-Jaworowska Z and Gambaryan PP 1994. Postcranial anatomy and habits of Asian multituberbulate mammals. Fossils & Strata 36:1-92.
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2010. In defence of parallel interphalangeal lines. Historical Biology iFirst article, 2010, 1–6 DOI: 10.1080/08912961003663500
Wible JR Rougier GW 2000. Cranial anatomy of Kryptobaatar dashzevegi (Mammalia, Multituberculata), and its bearing on the evolution of mammalian characters. Bulletin of the American Museum of Natural History 247:1–120. doi:10.1206/0003-0090(2000)247<0001:CAOKDM>2.0.CO;2.

wiki/Kryptobaatar