The Archosauria according to the U of Maryland website

The University of Maryland website on the Rise of the Dinosauria includes the following cladogram (Fig. 1) which pretty much follows paleo traditions. Note the proximal position of pterosaurs to ‘Dinosauromorpha’ and the distant position of crocodylomorphs, which makes room for many intervening taxa to be considered archosaurs (= birds + crocs).

Figure 1. The Archosauria according to the University of Maryland. Here pterosaurs are close to dinosaurs.

Figure 1. The Archosauria according to the University of Maryland. Here pterosaurs are close to dinosaurs. Click to enlarge.

By contrast
in the large reptile tree, pterosaurs nest far from dinosaurs and crocs nest alongside them. So there are no intervening taxa between dinosaurs and crocs (Fig. 2). And there are no odd nesting partners here, like pterosaurs nesting with taxa with small hands and tiny fingers and no toe 5, etc. etc

Figure 2. Same cladogram rearranged to more closely match the large reptile tree. Note how, even at this scale, the gradual evolution of dinosaur traits is not interrupted by the odd morphology of pterosaurs. And how the basal bipedal crocs nest close to the basal bipedal dinos. Click to enlarge. 

Figure 2. Same cladogram rearranged to more closely match the large reptile tree. Note how, even at this scale, the gradual evolution of dinosaur traits is not interrupted by the odd morphology of pterosaurs. And how the basal bipedal crocs nest close to the basal bipedal dinos. This tree is missing SO many taxa, it puts the reader into the position of having to believe the relationships, not observe them. Click to enlarge.

There is a clinging to tradition at the U of Maryland
that needs to be revisited. If students need to regurgitate these antiquated hypotheses in order to get a good grade, then what does that teach them at the university level?

Take a look at those key traits (in red) above (Fig. 1).

  1. Elongate pubes and ischia: also found in basal bipedal crocs and prodinosaurs, like the PVL 4597 specimen. Also in poposaurs, like Poposaurus an Turfanosuchus.
  2. Parasagittal stance and hinge-like ankle joint: also found basal bipedal crocs, like Scleromochlus and Terrestrisuchus. Sure pterosaurs have such a stance and ankle, but so do fenestrasaurs (tritosaur lepidosaurs) like Sharovipteryx.
  3. Ellongate tibiae and metatarsi; loss of bony armor: again, basal bipedal crocs and fenestrasaurs.
  4. The lower traits are synapomorphies.

Students,
put your thinking caps on. Ask the hard questions. Do the experiments yourself. This is Science. Don’t be satisfied with answers that don’t make sense and can’t be validated up and down the entire cladogram.

The large reptile tree does not use suprageneric taxa, as shown above. Only species- and specimen-based taxa are included there. All taxa demonstrate a gradual accumulation of derived traits. All subsets retain the tree topology. The tree has grown from 200+ taxa to 674 taxa with the same 228 characters lumping and splitting them to full resolution.

Plus pterosaurs and plus basal therapsids drive this taxon list into the 900s.

 

 

The origin and evolution of bats, part 4, an inverted thought experiment

There are no fossils
that currently document the origin of bats from non-volant carnivores or omnivores. Birds have a long fossil history. So do pterosaurs. For bats we have to conduct thought experiments in order to get from points we know: 1) a skilled arboreal omnivore like Ptilocercus, to 2) an Eocene fossil bat, like Icaronycteris (Fig. 1). It won’t help to have a Paleocene tooth, or skull. Those don’t change much in bat origins. We need to see, or visualize, the post-cranial body. Earlier forays into bat origins can be seen here, here and here.

Figure 1. GIF animation thought experiment on the origin and evolution of bats from a Ptilocercus-like omnivore.

Figure 1. GIF animation thought experiment on the origin and evolution of bats from an inverted Ptilocercus-like omnivore. Click to enlarge. Perhaps long fingers originally pulled maggots out of fruit and excellent hearing helped probate find where to dig.

We start with what we know

  1. All or most bats hang inverted
  2. The basal phylogenetic split is between Megachiroptera (fruit eaters) and Microchiroptera (insect eaters)
  3. Bat embryos probably recapitulate the development of those unknown phylogenetic predecessors, And they have big webbed hands early on.
  4. Bats don’t fly until their wings are nearly full size.
  5. What separates Ptilocercus from Icaronycteris is chiefly the size of the hands.
  6. There is no evidence that bats find their wings or wing size sexually attractive
  7. Caves are derived roosting spots. You have to fly in those to get a spot.
  8. Likewise, catching insects on the wing and echolocation follows the advent of flying, but listening to maggots munching fruit might have been a precursor skill.

The big question has always been
how do you get a flight stroke out of quadruped? Pterosaur and bird ancestors were both bipeds with strong hind limbs and they evolved wings as 1) gaudy secondary sexual traits; and 2) to aid in locomotion, especially up steep inclines (Heers et al. 2016 and references therein). The only way that bats were bipeds was inverted with weak hind limbs, which is a whole different story, or, in this case, a whole different thought experiment.

Figure 2. Pteropus, a fruit bat.

Figure 2. Pteropus, a fruit bat, has relatively shored clavicles and larger scapulae extending over most of the rib cage. The extremely long toes are derived. Parallel interphalangeal joints present on bat wings show the phalanges flex in sets.

Hypothetical stages in bat development

  1. Start with an agile arboreal omnivore like Ptilocercus, derived from long-legged arboreal carnivores in the Cretaceous/Paleocene, like Chriacus.
  2. Hanging fruit and the maggots therein can be attacked by likewise hanging on the supporting branch.
  3. The tiny hands of Ptilocercus could hold the fruit more steadily if the f fingers were longer. Maybe digging out maggots was aided by longer, thinner fingers.
  4. Webbing on even longer fingers would help trap juices, pieces, maggots from dropping out, and (see #6).
  5. At this stage the inverted biped no longer uses those hyper-elongate fingers for climging, so they are capable of being folded, not from the metatarsophalangeal joint, but at the wrist.
  6. In tropical forests bats use their wings as fans to cool themselves off (see video here), often after salivating on themselves for evaporative cooling. This is one of two pre-flight-stroke actions I have found.
  7. To rise from an inverted position on a branch, bats will flap vigorously (Fig. 3), which is the other pre-flight-stroke action.
  8. Mother bats wrap developing infants in their folded wings, but that doesn’t get them into the air.
  9. At a certain point, the pro-bat has wings that are capable of fanning the air, but incapable of flying. This is when the first branch-to-branch and tree-to-tree flapping leaps took place. If the pro-bat falls to the ground, it dies. Only successful arboreal flapping ‘acro-bats’ survive and improvements increase those odds.
Figure 1. Is this the origin of bat flapping. From an inverted position, this bat rises to horizontal by flapping, still clinging to its perch until release and flight. Click to open video.

Figure 3. Is this the origin of bat flapping. From an inverted position, this bat rises to horizontal by flapping, still clinging to its perch until release and flight. Click to open video.

In summary,
hanging pro-bats first developed long fingers to hold hanging fruit and perhaps remove maggots. Fanning for cooling could only develop with large webbed hands. Vigorous flapping from an inverted configuration is one solution to elevating the head and body. Letting go with the feet during this activity is the first awkward and potentially lethal stage to ultimately perfecting the flight stroke over many generations. The origin of flapping in bats is only a thought experiment at present with no other evidence currently available.

References
Heers AM, Baier DB, Jackson BE & Dial  KP 2016. Flapping before Flight: High Resolution, Three-Dimensional Skeletal Kinematics of Wings and Legs during Avian Development. PLoS ONE 11(4): e0153446. doi:10.1371/journal.pone.0153446
http: // journals.plos.org/plosone/article?id=10.1371/journal.pone.0153446

Huaxiagnathus: yet another basal tyrannosauroid!

Updated May 23, 2016 with a deeper maxilla posterior to the antorbital fenestra. This was needed, as pointed out by M. Mortimer, to house the tooth roots. I missed the splinter that made the difference and someday may try to trace the palatal elements, which I have avoided at present. 

Huaxiagnathus orientalis
(Hwang et al. 2004, Fig. 1) was originally considered a large compsognathid. The Hwang et al tree (now 12 years old) nested Huaxiagnathus with Compsognathus and Sinosauropteryx in the clade Compsognathidae, derived from a sister to Ornitholestes, and basal to therizinosaurs, alvarezsaurs, oviraptors, birds, and deinonychosaurs.

Figure 1. Huaxiagnathus in situ with reconstructed skull, pes, manus and pelvis. Note the relatively large pedal digit 3, the large hyoid, and the twisty lacrimal. Hwang et al. did not provide a reconstruction.

Figure 1. Huaxiagnathus in situ with reconstructed skull, pes, manus and pelvis. Note the relatively large pedal digit 3, the large hyoid, and the twisty lacrimal. Hwang et al. did not provide a reconstruction.

Here
in the large reptile tree Huaxiagnathus nests at the base of the tyrannosauroids, between Tianyuraptor + Fukuivenator and Zhenyuanlong. Yet, another heresy…

Hwang et al. reported the absence of a sternum. 
That’s odd because all current sisters have a sternum. The fossil was collected by farmers, but no preparator was mentioned. Perhaps there was a village preparator. After many tests  conducted by AMNH personnel, the fossil was determined to be genuine, singular and not a chimaera. Given the presence of both humeri where they are, the sternum should be between them. It is not, so one wonders if the sternum was removed by the preparators to expose the underlying humerus. A DGS tracing appears to show the remains of a posterior sternum (Fig. 2, magenta, contra Hwang et al.).

Figure 2. Pectoral region of Huaxiagnathus with various elements colored for clarity. The magenta bone appears to be posterior rim of a sternum, overlooked or considered an elbow by Hwang et al.

Figure 2. Pectoral region of Huaxiagnathus with various elements colored for clarity. The magenta bone appears to be posterior rim of a sternum, overlooked or considered an elbow by Hwang et al. A second overlay colorizes bits and pieces of the possible sternum extending toward the coracoids.

The Hwang et al. diagnosis reports: 
“Differs from other known compsognathids in having

  1. a very long posterior process of the premaxilla that overlaps the antorbital fossa,
  2. a manus as long as the lengths of the humerus and radius combined,
  3. large manual unguals I and II that are subequal in length and 167% the length of manual ungual III,
  4. a first metacarpal that has a smaller proximal transverse width ( i.e. “narrower”) than the second metacarpal and
  5. a reduced olecranon process on the ulna.”

Comments:

  1. The premaxilla doesn’t overlap the maxillary fossa, but tyrannosaurs have a similar long posterior process
  2. true! and no related taxa share this trait, even those with more bird-like morphologies
  3. okay… but that’s a pretty exact percentage for ungual three! (similar to Zhenyuanlong, though)
  4. if so, then just barely a smaller transverse width
  5. as in several basal tyrannosauroid sisters
  6. Not mentioned above, but those pedal proportions seem unique, with a dominant pedal digit 3. The hyoid is enormous. So few and so large are the maxillary teeth that they seem to be unusual, especially compared to the tiny teeth of Compsognathus. There seem to be many ossified stiffening element scattered throughout the vertebral column. Higher resolution should solve this problem.

Like tyrannosauroids
Huaxinagnathus had a short neck and large skull longer than the cervicals and just about as long as half the presacral length. The convex maxilla orients the premaxilla into an ‘up’ orientation. The quadratojugal, here broken into several parts, has a mushroom dorsal process that meets a squamosal ‘lid’. The lacrimal has the familiar tyrannosaur-ish in and out twist. The the maxillary teeth are BIG and few.

Figure 3. Huaxiagnathus skull with elements colorized and reconstructed in figure 4. Orignal tracing is in black outline. Many of the bones are broken.

Figure 3. Huaxiagnathus skull with elements colorized and reconstructed in figure 4. Orignal tracing is in black outline. Many of the bones are broken.

A reconstruction puts the elements
back into their in vivo positions (Fig. 4). Many of the bones are broken and had to be repaired. The scleral elements are scattered.

Figure 4. Huaxiagnathus skull and hyoid reconstructed. See figure 4b for other clade member skulls.

Figure 4. Huaxiagnathus skull and hyoid reconstructed. See figure 4b for other clade member skulls.

Basal theropod subset of the large reptile tree
shows the nesting of Huaxiagnathus in the basal tyrannosauroids (Fig. 5). Both Compsognathus specimens have a most recent common ancestor, with no intervening taxa. Huaxiagnathus, originally considered a compsognathid is one if the whole clade is considered the Compsognathidae. Otherwise, Only Struthiomimus and the Compsognathus holotype form a clade and are sisters. The CNJ79 specimen of Compsognathus is not the adult form of the holotype (contra Peyer 2006), but deserves a new generic name.

Figure 1. Basal theropod subset of the large reptile tree showing troodontids basal to birds and separate from dromaeosaurs.

Figure 5. Basal theropod subset of the large reptile tree showing the two Compsognathus specimens. Hauxiagnathus is a basal tyrannosauroid derived from a sister to Compsognathus.

So…
with every new taxon repairs do get made to the large reptile tree, but the tree topology does not change very often. The theropod subset just keeps growing without shifting around. You would think that if there were enough scoring mistakes the tree topology would change. The key thought here is that some repairs actually cement relationships. The repairs typically, but not always, remove misinterpreted ‘autapomorpies.’ For instance, the ilium of Zhenyuanlong was earlier misinterpreted as having a longer anterior process, which would be an autapomorphy for the clade. A reexamination revealed the relatively longer posterior process (Fig. 6). So, it’s true what they say about me, I don’t get it right the first time all the time.

Figure 6. Zhenyuanlong has a new ilium with a shorter anterior process.

Figure 6. Zhenyuanlong has a new ilium with a shorter anterior process that was earlier misinterpreted.

Huaxiagnathus further cements
the relationships of Zhenyuanlong, Tianyuraptor and Fukuivenator to the tyrannosaurs (contra Hone 2016) and Brusatte (2015). For its size, it looks like one (Fig. 7) with robust lower limbs, large teeth on a curved maxilla, a large head relative to the neck and torso. And don’t forget to picture this skeleton with lots of feathers as in Zhenyuanlong (Fig. 6).

Figure 7. Huaxiagnathus reconstructed in lateral view.

Figure 7. Huaxiagnathus reconstructed in lateral view, sans feathers.

References
Brusatte S 2015. Rise of the Tyrannosaurs. Scientific American 312:34-41. doi:10.1038/scientificamerican0515-34
Hwang SN. Norell MA, ji Q and Gao K-Q 2004. A large compsognathid from the Early Cretaceous Yixian Formation of China. Journal of Systematic Palaeontology 2(1):13-30.

wiki/Huaxiagnathus

The large French Compsognathus specimen

Updated May 23, 2016 with a new mandible. M. Mortimer pointed out correctly that I had traced two coincident mandibles as one. 

The less well-known
French specimen of Compsognathus corallestris (Bidar et al. 1972b; Peyer 2006; CNJ79) is a bit larger with a different morphology (Fig. 1) than the coeval smaller Bavarian Solnhofen specimen, Compsognathus longipes (Fig. 1 right). Dr. Peyer considers these two Late Jurassic theropods conspecific and representative of ontogenic rather than phylogenetic variation.

Figure 1. The large (from Peyer 2006) and small Compsognathus specimens to scale. Several different traits nest these next to one another, but at the bases of two sister clades. Note the differences in the forelimb and skull reconstructions here. There may be an external mandibular fenestra. Hard to tell with the medial view and shifting bones.

Figure 1. The large (from Peyer 2006) and small Compsognathus specimens to scale. Several different traits nest these next to one another, but at the bases of two sister clades. Note the differences in the forelimb and skull reconstructions here. There may be an external mandibular fenestra. Hard to tell with the medial view and shifting bones.

From the Peyer abstract:
“The absence of an external mandibular fenestra, dorsally fan-shaped dorsal neural spines with hook-shaped ligament attachments, and a  very short McI and a PhI-1, which is stouter than the radius distinguish compsognathids from other coelurosaurs. Anatomical and morphological characters of the Bavarian specimen of Compsognathus are nearly identical to those of the French specimen. The differences are related to ontogenetic or within-species variation or are caused by preservational factors. Therefore this study proposes that C. corallestris is a subjective junior synonym of Compsognathus longipes from Bavaria.”

You’ll note that “compsognathids” sensu Peyer are scattered throughout this large reptile tree subset of the Theropoda (Fig. 2). Sinocalliopteryx and Juravenator are widely considered compsognathids, yet both nest far from one another here.

I tested the ontogenetic hypothesis of Peyer
in the large reptile tree. Indeed, the two Compsognathus specimens do nest next to one another, but at the bases of two different clades.

The smaller Compsognathus specimen
nested with Struthiomimus, Ornitholestes, Microraptor and T-rex, among others.

The large Compsognathus specimen
nested with the oviraptorid, Khaan, Limusaurus, therizinosaurs, Sinosauropteryx and others. More derived clades include Eotyrannosaurus and other paravians such as dromareosaurids, troodontids and birds.

Figure 2. Compsognathus corrallensis nests close to the holotype smaller specimen, but at the base of the next clade, which includes oviraptors, therizinosaurs, Juravenator and Sinosauropteryx.

Figure 2. Compsognathus corrallensis nests close to the holotype smaller specimen, but at the base of the next clade, which includes oviraptors, therizinosaurs, Juravenator and Sinosauropteryx. That means it is not the adult version of the smaller specimen.

The new reconstruction
of the large Compsognathus skull is relatively shorter. Both the premaxilla and the dentary tip are oriented slightly down. The bones of the mandible slid apart during taphonomy. Put them back together to match the skull length and you might get a mandibular fenestra, as also seen in the smaller Compsognathus. The new skull reconstruction (Fig. 1) was created using DGS, not freehand as in the Peyer reconstruction.

Figure 3. DGS tracing of large French Compsognathus skull. These parts were used to make the reconstruction in figure 1. Only the left side and top elements were colorized.

Figure 3. DGS tracing of large French Compsognathus skull. These parts were used to make the reconstruction in figure 1. Only the left side and top elements were colorized.

Current traditional compsognathids include the following taxa

  1. Compsognathus
  2. Sinocalliopteryx
  3. Juravenator (some say yes, others say no)
  4. Sinornithosaurus
  5. Huaxiagnathus

In the large reptile tree the clade that includes Compsognathus now include the following taxa

  1. Compsognathus
  2. all ornithomimids, including Struthiomimus

References
Bidar AL, Demay L and Thomel G 1972b. Compsognathus corallestris,
une nouvelle espèce de dinosaurien théropode du Portlandien de Canjuers (Sud-Est de la France). Annales du Muséum d’Histoire Naturelle de Nice 1:9-40.
Ostrom JH 1978. T
he osteology of Compsognathus longipes. Zitteliana 4: 73–118.
Peyer K 2006.
A reconsideration of Compsognathus from the upper Tithonian of Canjuers, southeastern France, Journal of Vertebrate Paleontology, 26:4, 879-896,
Wagner JA 1859. Über einige im lithographischen Schiefer neu aufgefundene Schildkröten und Saurier. Gelehrte Anzeigen der Bayerischen Akademie der Wissenschaften 49: 553.

wiki/Compsognathus

Those two Houston Rhamphorhynchus specimens

Two Rhamphorhynchus specimens
housed in the Houstom Museum of Natural History were recently traced and reconstructed (Figs.1-5) I don’t know the museum numbers, but a request is in. Here we’ll refer to them as the wet wing specimen and deep cut specimen for reasons that will become obvious.

Figure 1. The HMNS wet wing specimen of Rhamphorhynchus. Note the narrow chord wing membranes and the perfect layout of the specimen, almost as if it was rebuilt.

Figure 1. The HMNS wet wing specimen of Rhamphorhynchus. Note the narrow chord wing membranes and the perfect layout of the specimen, almost as if it was rebuilt.

The wet wing specimen
was preserved in three dimensions, ventral view exposed. The matrix looks very odd for Solnhofen limestone. All the parts are laid out almost perfectly, as if they were shifted to their in vivo positions. The wing membranes are not like those of the Zittel specimen. They look like they were created out of wet matrix then allowed to set.  I didn’t know if this specimen is a chimaera or not so I ran the traits through phylogenetic analysis. Evidently it is not a chimaera because few to no traits are odd for its nesting.

Figure 2. The HMNS (1862?) wet wing specimen reconstructed.

Figure 2. The HMNS (1862?) wet wing specimen reconstructed.

The caption for the wet wing specimen is more confusing than informative. The text carries the flavor of HMNS curator and famous author/paleontologist, Dr. Robert Bakker.

Figure 3. The HMNS (1862?) wet wing specimen of Rhamphorhynchus along with its caption, rewritten in text below.

Figure 3. The HMNS (1862?) wet wing specimen of Rhamphorhynchus along with its caption, rewritten in text below.

The caption reads, “Bat-wings with Super-fingers. Pterodactyls first evolved in the Triassic, long before birds acquired their wings. Instead of feathers, ‘dactyls used bat-style wing of strong, elastic skin that stretched from the hand to the ankle.

Bats use four fingers to support their wings. ‘Dactyls are simpler.; the leading edge of the wing is connected to a single enlarged digit.

Breast-bones for Flight Power
‘Dactylus evolved wide breastbones and enlarged flanges for the chest muscles that powered flight. Extra strength came from the hind limb, which flapped up and down with each stroke.

Leading edge Flap and Trail-rudder
‘Dactyls evolved a ‘leading-edge flap,” similar to what is seen on modern airplanes. A spike of bone on the wrist could tighten a narrow strip of of wing skin along the front of the main wing and turn it up or down to manipulate lift and speed.

Rhamphorhynchus and other long-tailed ‘dactyls had a rudder built into the tail. Long, thin bone rods stiffened when the tail muscles tightened, while other muscles near the hip could flip the tail in any direction.”

Good grief!
This has to be confusing to the museum visitor. To look at it, the wing membranes clearly reach the elbows, not the ankles. On a more academic vein, the tail vane acted more like an arrow vane, keeping the tail in line while in the air, and acting like a secondary sexual trait while on the ground. It was not a rudder. Rudders rotate on an axis close to their maximum width. The leading edge “flap”in the text is the propatagium and was not manipulable. That’s an idea that has dropped out of favor, but once was out there. The propatagium simply opened taut whenever the wing fingers was extended. It prevented overextension of the elbow and a strong airfoil shape. And finally, cartoon characters are ‘Dactyls,’ not museum exhibits. It was cute when Bakker did it in his book. Not so much anymore, especially when the ‘Dactyl’ is not a pterodactyl-grade pterosaur.

Figure 4. The HMNS deep cut specimen of Rhamphorhynchus with tracings.

Figure 4. The HMNS deep cut specimen of Rhamphorhynchus with tracings on a more typical Solnhofen matrix bed .his specimen was deeply buried.

The HMNS deep cut specimen
This is a more typical Solnhofen matrix presentation and there is no doubt that all the bones were uncovered in their original positions from a single specimen. Imagine how little of this specimen was exposed on the surface when first discovered. As mentioned earlier, preparators know exactly where to dig in Solnhofen strata because the buried specimen produces a ghost-like bump in the upper bedding planes.

Figure 6. The HMNS deep cut specimen of Rhamphorhynchus reconstructed. Note the clear differences, showing the two Houston specimens were not conspecific.

Figure 6. The HMNS deep cut specimen of Rhamphorhynchus reconstructed. Note the clear differences, particularly in the feet and hands, showing the two Houston specimens were not conspecific.

Phylogenetic nesting sites
Neither of these two specimens are identical to any of the previously nested specimens in the large pterosaur tree/cladogram (awaiting museum numbers before that gets updated). The wet wing specimen nests with the Imhoff (with fish) specimen alongside the giant Rhamphorhynchus specimens, n81 and n82 (in the Wellnhofer 1975 catalog) and the Vienna juvenile earlier identified by phylogenetic analysis.

The deep cut specimen nests with the dark wing specimen of Rhamphorhynchus and its clade members, including the Washington University specimen here in St. Louis.

These specimens have not been published yet, so there are no references today.

July 8, 2016:
Dr. Bob Bakker at the HMNS wrote, “You can quote me as stating that the narrow wing, carved in relief, has no biological reality. And please do pass on to your readers that there is an etiquette to follow when publishing on specimens on public view. Art pieces are treated the same way.”

I wrote to the HMNS prior to the post seeking museum numbers regarding the display pterosaurs with no reply. If a specimen is on display, I take it that it is a specimen that will not be published or has already been published. More of a show piece. Apologies were offered.

Update on Tianyuraptor – and a few worthy YouTube videos

First Zhenyuanlong, then Tianyuraptor, Ornitholestes and finally Fukuivenator were recovered as taxa basal to tyrannosaurs — in contrast to traditional nestings by Brusatte and Hone. In the case of Tianyuraptor (Zheng et al. 2010), I followed the original tracing (which turned out to be neither as clear nor as accurate as needed) and created a reconstruction with a short neck, following the pattern of Zhenyuanlong (Fig. 2). The short neck of Zhenyuanlong gave my mind a prior ‘tradition’ or ‘bias’ permitted the acceptance of that short neck.

Fortunately,  M. Mortimer cautioned that
17 dorsals in Tianyuraptor was too high a number for theropods. 13 or 14 should be the maximum number for theropods with 5 sacrals, according to Mortimer. A subsequent DGS tracing of the fossil itself (Fig. 1) revealed that 17 was indeed too high.  Only 15 are currently considered to be dorsals. One dorsal had to be removed when a hole in the matrix between two dorsals was judged to not include a missing dorsal. More cervicals were recovered, more closely matching the number found in more primitive proximal taxa like Ornitholestes, Compsognathus and possibly Sinornithosaurus. Among theropods tested in the large reptile tree, only these taxa have more than 25 presacrals. Microraptor, also in this clade. lt has 25 pre-sacrals, which is still higher than most theropods and many more than in tyrannosaurs, which appear to lose several presacrals.

Figure 1. Tianyuraptor with DGS tracing locating more cervicals than before and reconstructed as a string of vertebral centra. The pelvis is also shown traced and reconstructed.

Figure 1. Tianyuraptor with DGS tracing locating more cervicals than before and reconstructed as a string of vertebral centra. The pelvis is also shown traced and reconstructed.

M. Mortimer also noted 
that Tianyuraptor does not have an anterior process on the pubic boot. And this is so. That process doesn’t appear until just barely in Zhenyuanlong. And I’m happy to make that change.

Unfortunately
neither of these changes in interpretation changes the nesting of Tianyuraptor or the large reptile tree topology, something M. Mortimer was evidently hoping to do. Note that a longer neck and more cervicals is found in the predecessor taxon, Ornitholestes (Fig. 2). So that character change just moved one node.

Figure 5. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Tyrannosaurus rex in the large reptile tree. Here Tianyuraptor has a much longer neck and a slightly shorter torso.

Figure 5. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Tyrannosaurus rex in the large reptile tree. Here Tianyuraptor has a much longer neck and a slightly shorter torso.

M. Mortimer also noted
that the scapulae of Zhenyuanlong are not dorsally expanded as in tyrannosaurs. I wondered why Mortmer wrote this, because I did not trace the scapulae with dorsal expansions. After taking another look at the photos, I see I have omitted the dorsal expansions hidden among the other bones. Here they are (Fig. 3), just like those in tyrannosaurs. Sorry, Mickey… and thanks!

Figure 3. Zhenyuanlong scapulae. Note the dorsal expansions, as in tyrannosaurs, peeking out from behind the other bones.

Figure 3. Zhenyuanlong scapulae. Note the dorsal expansions (in blue), as in tyrannosaurs, peeking out from behind the other bones. It’s a bit of a mess in both cases.

Mortimer also noted, Or for Zhenyuanlong, you reconstruct a tyrannosaur-like dorsally expanded quadratojugal, but it actually has a dromaeosaurid-like quadratojugal with a narrow dorsal process and long posterior process as seen and labeled in the paper’s figure 2.” 

Figure z. The skull of Zhenyuanlong with DGS tracings identifying the quadrate, quadratojugal and squamosal different from the original identifications.

Figure z. The skull of Zhenyuanlong with DGS tracings identifying the quadrate, quadratojugal and squamosal different from the original identifications.

To which I replied, “The back of the skull is such a mess that Lü and Brusatte opted to avoid identifying any bones there. What Lü and Brusatte identify as a right anlgle quadratojugal I identified as two bones, the horizontal rim of the surangular and a vertical slender  bone with an expanded base that appears to be the broken jugal ramus of the quadratojugal, which currently lacks a jugal ramus if all identifications are correct. I can see how that bone could be identified as a quadratojugal as it was by Lü and Brusatte. They identified the top of the quadratojugal as the quadrate, but that would be a very short quadrate. They did not identify the bone inside the surangular, which I identified as the quadrate. It fits the skull reconstruction and looks like a tyrannosaur quadrate. They key to resolving this argument may be higher resolution images and a disassembly of the Zhenyuanlong skull, either by hand or digitally, to identify all the bones properly. The rest of the skeleton (except the stiffened tail) more parsimoniously nests with tyrannosaurs, so, being human, I lean that way on skull bone IDs.”

On a more entertaining tyrannosaur note, 
there is a wonderful 2013 YouTube video by animator Teddy Cookswell showing the misadventures of a hatchling T-rex that is very well done. Find it here or click on the image (Fig. 4).

Figure 2. Click to animate video by Teddy Cookswell of T rex hatchling.

Figure 4. Click to animate video by Teddy Cookswell of T rex hatchling. Please ignore the anterior pteroids and flapping wing membranes of the pterosaur, minor problems with an otherwise wonderful depiction.

And finally
There’s another YouTube video promoting a new biography of Léon Foucault, inventor of the gyroscope and Foucalt pendulum, and the man who proved the Earth rotates by demonstrating this with a pendulum. The author, Amir Aczel and his book, “Pendulum: Leon Foucalt and the Triumph of Science,” provide some interesting insights into the acceptance of new ideas by the mathematics and science communities — and that’s why I bring it up here.

Aczel reports on all the dismissals Leon Foucault received after showing the Earth turned by using a pendulum — and by providing the formula for determining the length of time a pendulum would take to complete a circuit depending on its latitude on the Earth (24 hours at the pole, never at the Equator, 32 hours at Paris). Foucault was not considered to be either a scientist or a mathematician by the science and math elite. So his reports and results were dismissed by others. Foucault was an engineer and built the first apparatus that allowed the pendulum to swing continually and without building up torque in the line, both of which enabled his experiment to succeed.

The questions arose from the audience, would today’s scientists also look askance at such non-conformists? Aczel replied, “Yes.” As an example he cited the case of Swiss astronomer Michel Mayor who discovered the first extra solar planet in 1995 after many astronomers said 51 Pegasi would not have a planet because they tested it already. Mayor ignored conventional wisdom and found the planet. I don’t think that example actually illustrated the question, because Mayor was not dismissed after his discovery, rather he won awards (astronomy is different than paleontology, as we noted earlier). But Mayor’s urge and ability to test conventional wisdom was present in Aczel’s example.
Aczel summarized, “It is human nature to not want to accept new beliefs. People who believe a certain way, tend to hold on to their beliefs.  I believe that astronomers and mathematicians don’t always like to change their views or accept somebody else’s good results when they think it’s their territory.” 

References
Zheng X-T; Xu X; You H-L; Zhao, Qi; Dong Z 2010. A short-armed dromaeosaurid from the Jehol Group of China with implications for early dromaeosaurid evolution. Proceedings of the Royal Society B 277 (1679): 211–217.

C-Span video of Amir Aczel

New fossil bats video from the Royal Tyrrell Museum: Dr. Gregg Gunnell

The origin of bats
has been THE hottest topic here at the PterosaurHeresies.Wordpress.com blogsite. See earlier posts here, here and here.

“Fossils of the Night – The History of Bats Through Time” is a new YouTube video (53 minutes) brought to you by Dr. Gregg Gunnell from Duke University, speaking in the Royal Tyrrell Museum series on prehistoric topics.

Dr. Gunnell reports:

  1. only one extinct genus of fruit bat/flying fox
  2. 40+ extinct microbats (all echo-locators)
  3. Bats not close to primates, but with carnivores, hooved mammals, etc. (pretty broad!)
  4. Origin to 65 mya according to molecular clock
  5. Appear at 52 mya. We lack bat fossils from the Paleocene
  6. 11 extinct families of bats
  7. Icaraonycteris and Onychonycteris are two of the oldest known fossil bats. (Eocene, 52 mya) complete
  8. Messel bats (48 mya) more or less complete.
  9. More recent bats are bits and pieces, mostly dental taxa
  10. None of these are directly related to living families
  11. By the Pliocene nearly all modern taxa are known from fossils.
  12. Brachial index (forelimb/hindlimb ratio) midway between non-volant and flying mammals.
  13. CT scans of the teeth were made. All the inner halves of the teeth are crushed into small pieces.
  14. Certain lacewings, both extinct and extant, have a auditory organ on the wings that enables them to detect bat sonar. They stop flying when bats are detected.
  15. Bats have a low metabolism for their size. They live for up to 40 years.
  16. Smaller size increases wingbeat and sonar frequencies
  17. ‘Phyletic nanism’ describes body size decrease, island dwarfism. Onychonycteris was 38-40g. Microbats run about 14g.
  18. Gunnell reports on Yi qi, accepting the patagium/extra wrist bone hypothesis, which was falsified here.
  19. The origin of bats — Dr. Gunnell reports we don’t know what came before Onychonycteris.
  20. Nice morph video (5 seconds) of an inverted mammal on a tree trunk turning into a bat at the very end of the presentation.

This origin agrees with the large reptile tree,
which pulls both bats and primates out of carnivores. Here (Fig. 1) the extant Ptilocercus is employed as a model bat ancestor morphotype.

Figure 4. Ptilocercus, Icaronycteris and a hypothetical transitional taxon based on the ontogenetically immature wing of the embryo Myotis. If you're going to evolve wings it looks like you have to stop using them as hands early on. Note in the bat embryo there is little indication of inter-metacarpal muscle. That area looks identical to the web.

Figure 1. Ptilocercus, Icaronycteris and a hypothetical transitional taxon based on the ontogenetically immature wing of the embryo Myotis. If you’re going to evolve wings it looks like you have to stop using them as hands early on. Note in the bat embryo there is little indication of inter-metacarpal muscle. That area looks identical to the web.

 

 

Biseridens and Phthinosuchus – two misunderstood therapsids

Biseridens, according to Wikipedia,
“is the most basal genus of anomodont therapsid.”

Not so,
according to the large reptile tree (Fig. 3), which nests Biseridens (Fig. 1, Li and Cheng 1997; Liu, Rubidge and Li 2009) far from anomodonts, between Archaeosyoson and Jonkeria and kin among the Tapinocephalia.

Figure 1. Biseridens and Phthinosuchus, two related therapsids that have been giving paleontologists fits.

Figure 1. Biseridens and Phthinosuchus, two related therapsids that have been giving paleontologists fits.

Phthinosuchus, according to Wikipedia
“is the sole member of the the family Phthinosuchidae. It may have been one of the most primitive therapsids.” Not so, according to the large reptile tree (Fig. 2) where Phthinosuchus (Fig. 1, Efremov 1954) nests between Eotitanosuchus and ArchaeosyodonBiseridens at the base of the Dinocephalia.

So traditional nestings seem to be a little behind the times.
According to Liu, Rubidge and Li 2009, “Synapomorphies that distinguish Biseridens as an anomodont and not an eotitanosuchian as previously described: short snout (1); dorsally elevated zygomatic arch (2) and septomaxilla lacking elongated posterodorsal process between nasal and maxilla (3). The presence of a differentiated tooth row (4); denticles on vomer, palatine and pterygoid (5); contact between tabular and opisthotic (6); lateral process of transverse flange of pterygoid free of posterior ramus and absence of mandibular foramen exclude it from other anomodonts (7). Cladistic analysis indicates Biseridens to be the most basal anomodont (8).

Well, according to the large reptile tree…

  1. Eotitanosuchus has a long snout because it is basal to the clade of long snouted basal gorgonopsians and therocephalians. Biseridens ancestors, like Phthinosuchus, and Archaeosyodon, never had a long snout.
  2. the zygomatic arch (squamosal principally) is not dorsally elevated in the fossil (Fig. 1)
  3. sisters likewise lack this septomaxilla trait
  4. the dual rows of post-canine teeth and the large orbit in Biseridens are autapomorphies that distinguish it from sisters
  5. Denticlaes are also found on the palate of Phthinosuchus. I don’t have data for closer sisters.
  6. I don’t have comparable occipital data here
  7. I don’t have comparable palatal data here
  8. Be careful when a taxon nests as the ‘most basal’ to any clade without many more basal taxa on the inclusion list. As in another purported basal synapsid taxon, Caseasauria, it turns out that Biseridens actually nests elsewhere (Fig. 2).

Learn more about basal anomodonts here.

Figure 3. Basal therapsid tree.

Figure 2. Basal therapsid tree. Note the nestings of Phthinosuchus and Biseridens far from where tradition al paleontologists have been saying. I think more taxa near the base of the tree make tis tree distinct. Note the weak bootstrap scores at the nodes splitting Suminia from Venjukovia and splitting the basal dromasaurs.

 

References
Efremov IA 1954, The fauna of terrestrial vertebrates in the Permian copper sandstones of wester Cis-Urals: Travaux de I’institut Paleozoologique de l’Academie des Sciences de l’URSS, v. 54, 416pp.
Li J and Cheng Z 1997. First discovery of eotitanosuchian (Therapsida, Synapsida) of China. Vertebr. Palasiatica 35, 268–282.
Liu J, Rubidge B and Li J 2009. A new specimen of Biseridens qilianicus indicates its phylogenetic position as the most basal anomodont. Proceedings of the Royal Society B 277 (1679): 285–292. online

wiki/Biseridens
wiki/Jonkeria
wiki/Phthinosuchus

 

Rise of the Tyrannosaurs by Stephen Brusatte

Revised May 15, 2016 with a longer neck for Tianyuanlong, more like that of its outgroup sister, Ornitholestes. Grateful to M. Mortimer for suggesting I take another look at it, but the objections raised were not valid for this taxon. 

Scientific American has published several articles devoted to dinosaurs. “Rise of the Tyrannosaurs – New fossils put T.rex in its place” (Brusatte 2015) is one of the latest (Fig 1).

Figure 1. Rise of the Tyrannosaurs by Stephen Brusatte, Scientific American

Figure 1. Rise of the Tyrannosaurs by Stephen Brusatte, Scientific American. Cover art by James Gurney of Dinotopia fame.

From the online access page:

  • Paleontologists have known about T. rex and other giant tyrannosaurs for decades. But they were unable to piece together when the tyrannosaurs originated and what they evolved from because they lacked the fossils to do so.
  • Recent fossil finds have gone a long way toward filling those gaps in scientists’ understanding of this iconic group.
  • Together these discoveries reveal that tyrannosaurs have surprisingly deep—and humble—evolutionary roots.
  • Furthermore, the group encompasses a far greater diversity of forms than experts had anticipated—including some with truly bizarre anatomical features (Fig. 2).
Figure 2. Tyrannosaur ancestors according to Brusatte, artwork by Todd Marshall. Those on the left are actually closer to allosaurs and spinosaurs. Drag to desktop to enlarge.

Figure 2. Tyrannosaur ancestors according to Brusatte, artwork by Todd Marshall. Those on the left are actually closer to allosaurs and spinosaurs. Click to enlarge.

Despite the fantastic artwork,
the taxa in ‘the rise’ are actually basal to allosaurs and spinosaurs, not tyrannosaurs (Fig. 1), according to the large reptile tree (Fig. 4). Some of the ancestors recovered in the large reptile tree, like Zhenyuanlong, had extensive wing feathers (Fig. 3), which actually makes the ancestry of T-rex more interesting. And it makes the little hands of T-rex, vestigial wings.

Figure 3. Tyrannosaur ancestors to scale according to the large reptile tree. Drag to desktop to enlarge.

Figure 3. Tyrannosaur ancestors to scale according to the large reptile tree. Click to enlarge.

Here’s the subset of the large reptile tree
focusing on basal theropods (Fig. 4). Note how Proceratosaurus, Guanlong and Dilong could be considered basal to tyrannosaurs, but really they are closer to allosaurs in this cladogram. I think the mistake may lie, once again, in taxon exclusion, but also to misinterpretation.

Figure 4. Subset of the large retile tree focusing on theropods. Note the green taxa. While technically basal to tyrannosaurs, this clade is actually closer to allosaurs and spinosaurs. And the Brusatte text does not consider Zhenyuanlong, Tianyuraptor, Fukuiraptor and Ornitholestes.

Figure 4. Subset of the large retile tree focusing on theropods. Note the green taxa. While somewhat basal to tyrannosaurs, this clade is actually closer to allosaurs and spinosaurs. And the Brusatte text does not consider Zhenyuanlong, Tianyuraptor, Fukuiraptor and Ornitholestes.

We first learned about T-rex ancestors
(according to the large reptile tree) here, here, here and here. Here are Zhenyuanlong and kin again (Fig. 5), the more parsimonious ancestors of T-rex.

Figure 2. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Fukivenator at the base of the tyrannosaur clade.

Figure 5. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Tyrannosaurus rex in the large reptile tree. See how those little arms are actually vestigial wings?  The short back, long legs, large head are all tyrannosaur traits.

References
Brusatte S 2015. Rise of the Tyrannosaurs. Scientific American 312:34-41. doi:10.1038/scientificamerican0515-34

See a video on the production of the cover art and a peek inside the James Gurney studio here.

Learn more about artist Todd Marshall here.

Maybe Anomocephalus had canine fangs, too!

Two dicynodont-mimics,
Tiarajudens (UFRGS PV393P, Cisneros et al. 2011) and Anomocephalus (Modesto et al. 1999) were discovered in the last few two decades. Tiarajudens had sharp teeth and a fang/canine/tusk. Anomocephalus had flat teeth and apparently no tusk (Fig. 1).

Working from the published tracing
I put the scattered teeth of Anomocephalus back into the jaws and discovered that maybe there is a tusk/fang in there, too (Fig. 1). If valid, the fang was broken in half during typhonomy, so it became the same length as the other teeth, all of which had narrow roots, unlike the fang.

Figure 1. Anomocephalus in situ and reconstructed. Apparently a fang/canine/tusk was hiding among the broken teeth.

Figure 1. Anomocephalus in situ and reconstructed. In situ image from Modesto et al. 199. Apparently a fang/canine/tusk was hiding among the broken teeth.

Tiarajudens and Anomocephalus
are considered middle Permian primitive herbivorous anomodonts by the author(s) of Wikipedia, who also suggest they were ancestral to dicynodonts. By contrast, the large reptile tree (Fig. 2)  nests Tiarajudens and Anomocephalus in a clade close to, but separate from dicynodonts (Fig. 2).

Figure 3. Basal therapsid tree.

Figure 3. Basal therapsid tree. Note the nesting of the Anomodontia and the dicynodonts here, both derived from smaller dromasaurs.

According to the LRT, the ancestors of dicynodont mimics were 
Venjukovia and Otsheria. The ancestors of dicynodonts include Suminia, a late-survivor of an early radiation. Both were derived from smaller dromasaurs (Fig. 3).

Figure 3. Venjukoviamorphs include the dicynodont mimics, Tiarajudens and Anomcephalus. now with long canines.

Figure 3. Venjukoviamorphs include the dicynodont mimics, Tiarajudens and Anomcephalus, the latter now with mid-length canines. The Anomocephalus drawing is modified from Modesto et al. 1999 and appears to have certain problems.

References
Cisneros, JC, Abdala F, Rubidge BS, Dentzien-Dias D and Bueno AO 2011. Dental Occlusion in a 260-Million-Year-Old Therapsid with Saber Canines from the Permian of Brazi”. Science 331: 1603–1605.
Modesto S, Rubidge B and Welman J 1999. The most basal anomodont therapsid and the primacy of Gondwana in the evolution of the anomodonts. Proceedings of the Royal Society of London B 266: 331–337. PMC 1689688.