Early evolution of archosaurs – SVP abstract 2016

Nesbitt et al. 2016 discuss the early evolution of bird-line archosaurs.

From the Nesbitt et al. abstract:
“Bird-line archosaurs (= Avemetatarsalia, the clade containing dinosaurs, pterosaurs, and their kin) (1) had their origin in the Triassic Period. However, that origin is poorly documented (2) as fossils from their early evolutionary history are extremely rare and  consist mostly of postcrania. (3) Here, we report the discovery of a new reptile (femoral length = 17 cm) (4) from the lower portion of the Middle Triassic Lifua Member (Manda beds) of the Ruhuhu Basin, southwestern Tanzania. Material referred to the new taxon includes a partial skeleton of a single individual including cervical, trunk, and caudal vertebrae, pectoral, pelvic, forelimb, and hind limb material (= ‘Teleocrater’ of A. Charig), and parts (skull elements, vertebrae, pectoral, pelvic, and limb elements) of a minimum of three individuals collected from a bonebed discovered in 2015 very close to Charig’s original partial skeleton. Character states of the limbs, vertebrae, and ilium indicate a close relationship with early dinosauromorphs including: elongated cervical vertebrae, an ilium with a slightly concave ischial peduncle and clear anterior crest, a weakly developed anterior trochanter of the femur, an anteriorly compressed fibula with long strap-like iliofibularis crest, and absence of osteoderms (5). Many character states suggest that the new reptile taxon falls outside of the pterosaur-dinosaur clade (= Ornithodira). (6) However, the distributions of some of these character states at the base of Archosauria are unclear and some character states of the new taxon suggest a more basal relationship outside Archosauria (e.g., absence of two medial tubera of the proximal femur). No matter the position within or outside Archosauria, the new Lifua taxon shares seemingly unique character states with the poorly known Dongusuchus from the Middle Triassic of Russia (known from femora) and Yarasuchus from the Middle Triassic of India (known from partial skeletons), rather than with other archosauriforms. As a result, these forms appear to represent a globally distributed clade of early diverging avemetatarsalians. (7) The larger body size of the Manda form and its potential phylogenetic position outside of pterosaurs and dinosauromorphs indicates that there was a size decrease at the origin of Ornithodira. (8) This new taxon, and other new discoveries from the Middle to Late Triassic, are elucidating the sequence of character acquisitions in Avemetatarsalia and fill a crucial gap in the evolutionary history that led to the flourishing of dinosaurs later in the Mesozoic”. (9)

Notes

  1. Avemetatarsalia is a parphyletic clade or a junior synonym of the clade Reptilia because pterosaurs do not nest with dinosaurs and archosaurs in the LRT. Evidently taxon exclusion bias keeps Nesbitt et al. from considering fenestrasaur, tritosaur lepidosaurs as pterosaur ancestors. Only crocs and dinos comprise the Archosauria in the LRT. Like Dr. Naish, this clade of paleontologists are not exploring all the possibilities offered by a large gamut analysis, but opting to stay with traditional untested taxon lists.
  2. In the LRT the origins of all reptilian clades are well-documented going all the way back to basal tetrapods.
  3. Bogus claim, probably based on the mistaken assumption that headless Lagerpeton is basal to dinos. The origin of dinos is documented here.
  4. Similar in size to Lewisuchus, a pro-dinosaur.
  5. Some ‘dinosauromorph traits’ are in contention based on the inclusion set and recovered taxa basal to dinos.
  6. The ‘Ornithodira‘ is an invalid clade, or at the least, a junior synonym for ‘Reptilia’ in the LRT.
  7. Yarasuchus nests with a variety of genera in a clade between Rauisuchidae and Archosauria in the LRT.
  8. Indeed there was a size decrease at the origin of pterosaurs and at the origin of dinosaurs, but they had separate origins.
  9. If related to Yarasuchus, the new taxon is indeed distantly related to the origin of archosaurs, which included Gracilisuchus and the PVL specimen attributed to Gracilisuchus, both derived from sisters to the much larger Decuriasuchus and Turfanosuchus. The purported ‘gap’ reported by Nesbitt et al. appears to be because they are looking at the wrong outgroup taxa due to taxon exclusion in their phylogenetic analysis.
References
Nesbitt SJ, Butler RJ, Barrett PM, Stocker MR, Sidor CA, Angielczyk KD, Ezcurra MD and Smith RM 2016. The early evolution of bird-line archosaurs: a possible new clade of globally distributed avemetatarsalians just outside the dinosaur-pterosaur split. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.
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Is this the origin of baleen?

 

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 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 desmostylian taxa takes us to the toothless, baleen endowed whales.

It’s only a guess…
but given the odd and large gap between the upper and lower jaws of Paleoparadoxia (Fig. 1), together with the loss of all teeth between the anterior and posterior ones, that gap might have been filled with the genesis of baleen in this sister to the Mysticeti whales. Note the canine (orange) is here aligned with the maxilla, essentially out of service. The anterior teeth make ideal scoops. The posterior teeth are flat grinders. The jaws are broader than tall, providing a wide space for a larger tongue. The naris is dorsally placed, enabling Paleoparadoxia to remain submerged.

As noted earlier, toothed whales had a separate origin among the tenrecs.

PS
Better data just came out today on the geologically oldest Archaeopteryx #12, which I have updated here. The new data shifted the nesting by one node, to the base of the Scansoriopterygidae and thus it still remains very close to the ancestry of all living birds.

U of Leicester is seeking a pterosaur tracker.

Don’t let your academic ‘foot’ get caught in this trap.

This post arose
from an online want ad for a student pterosaur tracker posted by Dr. Dave Unwin and his team (see below) at the University of Leicester, England. Earlier we looked at a similar ad seeking a student who could find evidence for the invalidated pterosaur forelimb launch hypothesis. This new ad appears to be similarly doomed by conclusions drawn before the first student applies for this solicitation.

What is it about the English paleontology system
that promotes single-minded and undocumented thinking when it comes to pterosaurs? We’ve seen hyper-biased papers from Hone and Benton (2007, 2009), hyper-biased critiques from Dr. Naish, and pterosaur books authored by Dr. Unwin and Dr. Witton that ignored pertinent studies. Several English PhDs also supported the invalidated and unsupported anterior pteroid hypothesis. All seem to hold that pterosaurs are archosaurs, despite a complete lack of evidence and outgroups for that assertion and plenty of evidence for a lepidosaur tritosaur fenestrasaur origin, that they systematically ignore. All seem to support the invalidated bat-wing, deep-chord pterosaur wing fantasy that finds no evidence in the fossil record. This group holds to the outmoded notion that sparrow- and hummngbird-sized Solnhofen pterosaurs are juveniles, which is easy to dismiss on several grounds. There may be a few more stumble blocks I’ve failed to list here, like isometric growth in pterosaurs.

If you are a student of pterosaurs,
try to avoid the influence of this antiquated and conjoined bastion of pterosaur workers. The text of their want ad demonstrates that, like an earlier solicitation, you will have to arrive at their odd conclusions and support their invalid hypotheses. Rather than that, keep to independent thinking. It may prove to be key to understanding pterosaurs. Follow the data. I did so in my spare time. You can do it, too.

Here’s the ad
(see below in italic blue) with notes added [in brackets[.

Title:
The tracks of pterosaurs, and their implications for pterosaur palaeoecology and evolution 

Supervisory team
David Unwin, School of Museum Studies, University of Leicester (dmu1@le.ac.uk)

Mark Purnell, Department of Geology, University of Leicester (map2@le.ac.uk)
Richard Butler, School of Geography, Earth & Environmental Sciences, University of Birmingham
Peter Falkingham, School of Natural Sciences and Psychology, Liverpool John Moores University
Brent Breithaupt, 812 S. 13th St., Laramie, WY 82070 USA

From their online ad:
“Pterosaurs, Mesozoic flying reptiles, were long considered to have been almost exclusively confined to aerial niches, with only limited mobility when on the ground (Unwin, 2005). [1] Two lines of evidence have challenged this view. (1) A rapidly accumulating and increasingly diverse pterosaur track record (pteraichnites) that spans more than 80 million years. (2) Digital modelling, based on skeletal remains and tracks, of pterosaur’s terrestrial locomotory abilities. These studies show that pterosaurs used a flat-footed, four-legged, but nevertheless highly efficient, stance and gait. [2] They have also uncovered some unexpected behaviours, such as a quadrupedal launch, [3] that point to a far more effective ability to take-off and land than previously suspected. These new findings suggest that pterosaurs played a much bigger role in Mesozoic terrestrial communities than previously realised (Witton, 2013), but the extent and evolutionary significance of this phenomenon remains unclear and controversial. [4]

Notes

  1. This is only one of Dr. Unwin’s bogus hypotheses based on his invalidated idea that the hind limbs of basal pterosaurs were encumbered by a uroptagium that bound them together and bat-like deep-chord wings tied the legs to the wings. No pterosaur tracks show limited mobility. No fossil evidence documents either membrane structure.
  2. Ignored studies (Peters 2000a, 2010, 2011) and many pterosaur tracks indicate that plantigrade quadrupedal pterosaurs are restricted to certain clades, typically while beach combing, and that all pterosaurs were fully capable of bipedal locomotion and launch. Some pterosaurs were digitigrade, as demonstrated by their tracks and their parallel interphalangeal lines (Peters 2000. 2011).
  3. Bogus. No evidence in the track record. Click here, here and here for counter evidence.
  4. A bigger role? How do you answer that question?

“This project will use a multidisciplinary approach to reassess the contribution of pterosaurs to Mesozoic continental biotas and their impact on co-evolving groups such as early birds (Benson et al, 2014). New techniques including photogrammetric ichnology will form part of the first systematic analysis of the pterosaur track record. [1] This work will generate a range of data sets that capture fine detail of prints and tracks that can be combined with contextual data including sedimentology, stratigraphy and associated ichnological and body fossil evidence.

Notes

  1. The Unwin team is ignoring the actual first systematic analysis of the pterosaur track record, published in Ichnos five years ago (Peters 2011). Perhaps they ignore it because that ‘track record’ documented bipedalism, digitigrady and other ‘unapproved’ pterosaur activities and configurations.

“These data sets will underpin three complementary strands of the PhD: (1) reconstruction of the locomotory styles and abilities of pterosaurs (stance, gait, speed, take-of and landing modes) based on key sites in the USA and Europe. (2) The first comprehensive integration of the ichnological and body fossil record of pterosaurs via 3D digitisation of prints and well preserved skeletal remains. (3) Identification and reconstruction of specific behaviours (e.g. feeding, flocking) set within current interpretations of the palaeoenvironments in which they occurred.

Results of these three studies will be combined with data on the relationships and temporal and biogeographic distribution of pterosaurs to determine the extent to which they contributed to Mesozoic terrestrial biotas and influenced the evolution of contemporaneous groups such as birds.

 

Standing Pteranodon

Figure 1. Bipedal and digitigrade Pteranodon. Both are unapproved by the Leicester team but supported by evidence found in ignored literature.

Methodology

“New approaches to collecting and interpreting prints and tracks including photogrammetry, pioneered by Breithaupt (e.g. Lockely et al., 2016) will be used to generate high fidelity 3D digital data sets based on key sites in the USA (Wyoming), France (Crayssac) and Spain (Asturias) that contain multiple individuals and exceptionally high quality impressions (Unwin, 2005; Witton, 2013).

Identification of track-makers will take advantage of our rapidly expanding knowledge of pterosaur skeletal anatomy and the possibility of highly accurate comparisons between digitised sets of tracks and 3D skeletal elements of the hand and foot. [1] This approach will be located within a well established phylogenetic framework developed by Unwin and others. [2] Digital models have been shown to be highly effective at constraining likely stance, gait, velocity and manoeuvrability for extinct taxa (Falkingham and Gatesy, 2014) and will be applied here to both ichnological and skeletal data. The reconstruction of behaviours, palaeoenvironments and the evolutionary history of pterosaur terrestrial palaeoecology, supervised by Butler, will use quantitative approaches set within a phylogenetic framework. [3]

Notes

  1. This has already been done here and in Ichnos (Peters 2011), but testing, comparisons, confirmations and refutations are always welcome.
  2. Okay, if you’re going to do this, remember Unwin’s cladogram deletes all the small and tiny Solnhofen pterosaurs that form transitions between larger long-tails and larger short tails. He holds that Darwinopterus is the transitional taxon linking long-tails to short-tails, rather than an evolutionary dead end as shown here, along with several other odd phylogenetic nestings.
  3. Play by their rules and you will get their PhD. But should you play by their rules? They would love it if you could support their conclusions. Funny that they want an inexperienced and beholding student to do the work they are much better qualified to do, but won’t do. Also odd that they are not open to any and all solutions the data may deliver. After all, reporting conclusions AFTER the data comes in IS the scientific method.

Training and Skills

“Students will benefit from 45 days training throughout their PhD including a 10 day placement. Initially, students will be trained as a single cohort on research methods and core skills. Training will progress to master classes, specific to projects and themes. Specialist training will include identification and interpretation of pterosaur tracks and skeletal anatomy, supervised by Unwin, photogrammetry as applied to palaeoichnology, supervised by Breithaupt and Butler, and analysis of locomotion, supervised by Falkingham. The student will also receive training, supervised by Butler, in data base construction with a particular emphasis on the statistical analysis of palaeontological data.

Timeline

“Year 1: Familiarisation with literature, existing datasets and palaeoichnological techniques including photogrammetry. Fieldwork in the USA to collect pterosaur track data. Analysis of these data. Presentation at PalAss (UK) and SVPCA (UK).

Year 2: Fieldwork in Spain and France to collect pterosaur track data. Continued analysis of all track data and integration with body fossil record. Analysis of pterosaur locomotory styles. Publication and presentation at SVPCA (UK), EAVP (Europe).

Year 3: Synthesis of results on locomotory abilities, behaviours and palaenvironments. Develop evolutionary history of pterosaurs in terrestrial environments. Publication and presentation at SVPCA (UK), SVP (USA). Write and submit thesis. [9]

Notes

  1. Having already done much of the work they are asking, I wonder… would I be interested in getting a PhD from the Leicester team? No. I can’t bend that far. But seriously, GOOD LUCK to that candidate, whoever you may be. Negotiate for the scientific method before you sign on.

Partners and collaboration (including CASE)

“Dr Unwin has 30+ years experience of research on pterosaurs, holds extended datasets on pterosaur skeletal anatomy, and palaeoichnology and has access to key specimens that will be studied during this project. Prof Purnell has expertise in analysis of 3D surface datasets in the context of vertebrate ecology and function. Dr Falkingham has worked on fossil footprints for over a decade, using computational techniques including simulation (FEA, DEM, MBD) and digitization (laser scanning, photogrammetry) to study locomotion and footprint formation. Dr Butler has published widely on fossil reptiles, including pterosaurs, and has extensive experience in the application of quantitative approaches to analysis of palaeontological data. Dr Breithaupt has pioneered the development of photogrammetric ichnology, including its application to pterosaur tracks.

Further Details

Ideally, applicants should have a first degree in the geological or biological sciences and an aptitude for quantitative analysis. At Leicester you will join a dynamic group of researchers, PhD and Masters students developing novel approaches to the analysis of palaeoecology and evolution in fossil vertebrates.

Figure 1. Cartoon favorite Elmer Fudd tracking Bugs Bunny... or are those bipedal Pteraichnus tracks?

Figure 2. Cartoon favorite Elmer Fudd tracking Bugs Bunny… or are those bipedal Pteraichnus tracks?

Contact

D.M. Unwin
School of Museum Studies, University of Leicester,
19 University Road, Leicester LE1 7RF
Tel: +44 116 252 3946

Further reading

Benson, R.B.J. et al. 2014. Competition and constraint drove Cope’s rule in the evolution of giant flying reptiles. Nature Communications, 5, 3567, doi: 10.1038/ncomms4567.
Falkingham, P.L. & Gatesy S.M. 2014. The birth of a dinosaur footprint. Proc. Nat. Acad. Sci., 111, 18279-18284.
Lockley, M.G. et al. 2016. Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs. Nature: Scientific Reports, 6, nb 18952, doi:10.1038/srep18952.
Unwin, D.M. 2005. The Pterosaurs from Deep Time. Pi Press, New York, 347pp.
Witton, M.P. 2013. Pterosaurs: natural history, evolution, anatomy. Princeton University Press. 291pp.”

Forbidden and ignored references
Notably absent from the above published text and references are the following pertinent and peer-reviewed academic papers that do not support the hypotheses the prospective PhD candidate will have to labor under and support, regardless of the data and results.

Peters D 2000a. Description and interpretation of interphalangeal lines in tetrapods
Ichnos, 7: 11-41
Peters D 2000b. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293-336.
Peters D 2002. A new model for the evolution of the pterosaur wing – with a twist. Historical Biology 15: 277-301.
Peters D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 2007.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29(4):1327–1330.
Peters D 2010. In defence of parallel interphalangeal lines. Historical Biology iFirst article, 2010, 1–6.
Peters D 2011. A catalog of pterosaur pedes for trackmaker identification. Ichnos 18(2):114-141.

For abstracts of the above click here.

The desmostylian ?Behemotops is basal to the Mysticeti (baleen whales)

Backstory:
Traditional paleontology nests desmostyians with proboscidians (elephants) and sirenians. By contrast, the large reptile tree (LRT) nests desmostylians with hippos, anthracobunids, mesonychids and, pertinent to the present discussion, mysticetes (baleen whales) like Balaenoptera, the blue whale (Figs. 1, 2).

Figure 1. ?Behemotops cf. proteus as originally published, after lifting the posterior maxilla, with the addition of a warped Balaenoptera mandible and compared to Balaenoptera.

Figure 1. ?Behemotops cf. proteus as originally published, after lifting the posterior maxilla, with the addition of a warped Balaenoptera mandible and compared to Balaenoptera. Note the holotype of Behemotops, the short, toothy mandible at upper left, would never fit the long rostrum of the cf. specimen. The long and large humerus does not indicate that flippers were present here.

More backstory:
The desmostylian Behemotops proteus (Domning, Ray and McKenna 1986, Beatty and Cockburn 2015; Oligocene, 34-23 mya) was originally described on the basis of short, deep, but largely complete (missing the retroarticular process) and immature (unerupted molars) mandible USNM 244035 (Fig. 1). Another short, deep mandible with a distinctly different architecture and preserving the retroarticular process, USNM 244033 was also also assigned to this genus (Fig. 1), IMHO in error. Neither of these short mandibles appear to fit the long skull of another specimen tentatively assigned to this genus, Behemotops cf. proteus RBCM.EH2007.008.0001 (Fig. 1), which preserves the left half of much of the skull, but no mandible or cranium. An imaginary mandible has been supplied here (Fig. 1) based on phylogenetic bracketing and… it’s a good fit when warped to fit.

We need to come up with new genus
for the RBCM specimen.

This is more evidence
that extant whales are not monophyletic and that desmostylians are not extinct. They live on as baleen whales.

Figure 3. Blue whale (Balaenoptera musculus) skull and skeleton. Note the lack of a thumb goes back to Mesonyx.

Figure 3. Blue whale (Balaenoptera musculus) skull and skeleton. Note the lack of a thumb goes back to Mesonyx.

The resemblance of Behemotops
to the blue whale, Balaenoptera (Figs. 1, 2), is striking. Available post-cranial material for Behemotops (one relatively big humerus in Fig. 1) does not indicate flipper development (Fig. 2).

A phylogenetic fix is needed.
Earlier I reported on Janjucetus, which was considered the most basal mysticete whale by Fitzgerald 2006. Unfortunately revisiting the data indicates that leaf-toothed Janjucetus is now more closely related to Anthracobune, a small taxon known from more plesiomorphic teeth and most of a skull (no post-crania). Even so, with long-legged desmostylians now nesting between Janjucetus and Balaenoptera (Fig. 4), phylogenetic bracketing indicates that, despite their dorsal nares, Janjucetus and Anthracobune both had legs, like desmostylians, not flippers. So Janjucetus is not the most basal mysticete and its very distinct teeth are not precursors or placeholders to baleen.

Figure 5. Subset of the LRT, higher placental mammals with a focus on whales (yellow) and their ancestral clades, the Tenrecidae and Mesonychidae. Both are a fair distance from artiodactyls.

Figure 3. Subset of the LRT, higher placental mammals with a focus on whales (yellow) and their ancestral clades, the Tenrecidae and Mesonychidae. Both are a fair distance from artiodactyls. Note the new nesting of Janjucetus with Anthrobune and Behemotops with Balaenoptera.

References
Beatty BL and Cockburn TC 2015. New insights on the most primitive desmostylian from a partial skeleton of Behemotops (Desmostylia, Mammalia) from Vancouver Island, British Columbia. Journal of Vertebrate Paleontologoy 35(5):e979939: 15 pp.
Cockburn TC and Beatty BL 2009. A Partial Skeleton of Behemotops (Desmostylia, Mammalia) from Vancouver Island, British Columbia. Journal of Vertebrate Paleontology. 29 (3, Supplement): 1A–211A.
Domning DP, Ray, CE and McKenna, MC 1986. Two new Oligocene desmostylians and a discussion of Tethytherian systematics. Smithsonian Contributions to Paleobiology. 59. pp. 1–56.
Fitzgerald EMG 2006. A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales. Proceedings of the Royal Society B 273:2955-2963.

wiki/Janjucetus
wiki/Behemotops

Adding Pakicetus and Indohyus to the LRT

Pakicetus inachus (Gingerich & Russell 1981; middle Eocene; Figs. 1, 2) was originally hailed as “one of the oldest whales known anywhere.” Despite its lack of fins and flukes, Pakicetus was considered a whale based largely on the large posterior process of the periodic (near the ear region) and the thick, dense auditory bulla characteristic of all cetaceans. These traits indicate a underwater hearing and habitat even though Pakicetus had slender running legs and no flukes (Fig. 1). The resemblance of Pakicetus to Tenrec is striking — and remember some tenrecs, like Limnogale (Fig. 4), retained a long tail and are aquatic with webbed feet.

Figure 1. Odontoceti (toothed whale) origin and evolution. Here Anagale, Andrewsarchus, Sinonyx, Hemicentetes, Tenrec Indohyus and Leptictidium precede Pakicetus. Maiacetus and Orcinus are aquatic odontocetes.

Figure 1. Odontoceti (toothed whale) origin and evolution. Here Anagale, Andrewsarchus, Sinonyx, Hemicentetes, Tenrec Indohyus and Leptictidium precede Pakicetus. Maiacetus and Orcinus are aquatic odontocetes. Mysteceti (baleen whales) had a separate origin in Desmostylia.

The case for a tenrec ancestry for Odontoceti continues
Indohyus major (Fig. 1; Rao 1971, Thewissen et al. 2007; Eocene, 48 mya; 1m in length) was considered an artiodactyl, but nests in the large reptile tree (LRT with Leptictidium (Fig. 1) between tenrecs and odontocete whales. So the case for Leptictidium as a whale ancestor is strengthened with the addition of its sister Indohyus. The case for a traditional artiodactyl ancestor for whales is much diminished.

As we learned earlier, mysticete (baleen) whales are derived from desmostylians like Paleoparadoxia and Behemotops.

Figure 2. Skulls of transitional taxa between tenrecs and Odontoceti (toothed whales). These include Tenrec, Lepticitidium, Pakicetus, Rhodhocetus and Orcinus.

Figure 2. Skulls of transitional taxa between tenrecs and Odontoceti (toothed whales). These include Tenrec, Lepticitidium, Pakicetus, Rhodhocetus and Orcinus. The gradual accumulation of traits should be readily visible to the casual observer here.

One of the major problems with the artiodactyl-whale hypothesis
is this: artiodactyls are herbivores. Odontocetes are carnivores. Tenrecs eat a wide variety of animals.

Mystecete whales have no teeth, and did not evolve from carnivores. Although hippos, mesonychids and desmostylians all have big teeth, all are herbivores. Their largest teeth function more like tusks.

Figure 3. Indohyus skeletal elements nest between tenrecs and whales.

Figure 3. Indohyus skeletal elements nest between tenrecs and whales. While a sister to Leptictidium, the lines are more nearly equal in length here. We don’t know if Indohyus had claws or hooves. Leptictidium had long claws.

The mystery tenrec, Limnogale
No Limnogale skeletons are known to tenrec experts I contacted and little else is known of this extant, nocturnal, aquatic and long-tailed tenrec from Madagascar. It may hold a key place in the origin of whales. It appears to be plesiomorphic enough to do so, but it sure would be great to someday see a skeleton. The ears and eyes are small, the whiskers are bushy. Some tenrecs echolocate, but this taxon has been so little studied that I don’t know if it is an echolocator.

Figure 4. The rare and rarely studied web-footed tenrec Limnogale mergulus, which has a long tail, is nocturnal and aquatic.

Figure 4. Is this the true ancestor of odontocete whales? The rare and rarely studied web-footed tenrec Limnogale mergulus, which has a long tail, is nocturnal and aquatic. Both images copyright PJ Stephenson and used with permission.

Thewissen et al. 2007 report,
Indohyus shares a similar auditory bulla with cetaceans, not present in artiodactyls. “Other significant derived similarities between Indohyus and cetaceans include the anteroposterior arrangement of incisors in the jaw, and the high crowns in the posterior premolars.”

Well, those traits,
as you can see (Fig. 2) are also found in Tenrec and its sisters, but Thewissen et al. did not test tenrecs and any of the sisters recovered in the LRT, other than Andrewsarchus and Sinonyx. Indohyus had thick bones (osteosclerosis) which provided ballast for underwater activities. That it nests with Leptictidium (Figs. 1, 2) adds credence to the aquatic hypothesis advanced earlier here.

Figure 5. Subset of the LRT, higher placental mammals with a focus on whales (yellow) and their ancestral clades, the Tenrecidae and Mesonychidae. Both are a fair distance from artiodactyls.

Figure 5. Subset of the LRT, higher placental mammals with a focus on whales (yellow) and their ancestral clades, the Tenrecidae and Mesonychidae. Both are a fair distance from artiodactyls. Note the displacement of Janjucetus. Now it looks like it probably had legs. We’ll look at Behemotops soon.

Traditional paleontology
holds that “Mysticeti split from Odontoceti (toothed whales) 34 million years ago during the Eocene” and whales moved to the sea 50 mya (Rose 2001) having descended from hooved mammals. The present hypothesis (Fig. 5) holds that indeed Mysticeti were derived from hooved mesonychids/hippos/desmostylians. However, Odontoceti, the toothed carnivorous/piscivorous whales arise from clawed tenrecs, like Leptictidium (Figs, 1, 2). The hands and feet of the protowhale Artiocetus (Fig. 6) are well known and at least several of its unguals are claws — though much reduced and somewhat transformed due to their much reduced use on land and unknown extent of the webbing. At least one tenrec had webbed feet, Limnogale (Fig. 4). I know of no artiodactyls with webbed feet.

6. Artiocetus manus and pes had claw-like unguals, not hooves.

6. Artiocetus manus and pes had reduced claw-like unguals, not hooves. And Limnogale shows some tenrecs had webbed feet.

India/Pakistan and Madagascar
where odontocetes started and tenrecs now survive, were one continuous island that split apart some 88 million years ago… so there is no geographical barrier to the present hypothesis of tenrec and odontocete relations. But it does indicate the antiquity of the tenrec – odontocete split and relationship.

Australia and the Pacific rim
where mysticetes started and desmostylians were found is a much, much wider area. We find Desmostylia like Paleoparadoxia and Behemotops have only been found along the Pacific rim (Japan > Russia > Aleutian Islands > Pacific coast of North America  south to Baja California. A desmostylian sister, Anthracobune, is found in Eocene (40 mya) Pakistan. Janjucetus is found in younger 25 mya strata in Australia. A hippo and mesonychid sister, Ocepeia, dates to the Paleocene (60 mya) in Morocco, which is even further from Australia. So, the origin of the Mysticeti, appears to be somewhere along the Pacific rim.  More details tomorrow.

References
Gingerich PD and Russell DE 1981. Pakicetus inachus, A New Archaeocete (Mammalia, Cetacea) from the Early-Middle Eocene Kuldana Formation of Kohat (Pakistan). Contributions from the Museum of Paleontology, The Museum of Michigan. 25 (11): 235–246.
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, Williams EM, Roe LJ and Hussain ST 2001. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature 413:277-281.
Rose KD 2001. The Ancestry of Whales. Science. 293 (5538): 2216–2217. PDF
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/Indohyus
wiki/Pakicetus

Who ever said the giant otter shrew was a tenrec??

Everybody did and does.
Every reference (e.g. Wikipedia, EOL) you can find lists the giant otter shrew Potamogale velox (Du Chaillu 1860, Nicoll 1985) as a tenrec… and I don’t know why. But I’m willing to learn, if anyone can offer up an explanation based on phylogenetic analysis.

Until then…

Adding Potamogale to
the large reptile tree, nests it with Scutisorex the shrew (Fig. 2), not Tenrec the tenrec (Fig. 3).

Figure 1. Potamogale velox, the giant otter shrew nests with Scutisorex (Fig. 2), the hero shrew, in the large reptile tree.

Figure 1. Potamogale velox, the giant otter shrew nests with Scutisorex (Fig. 2), the hero shrew, in the large reptile tree.

Both shrews have
canine-like medial incisors and lack canine-like canines. Both have a skull shorter than half the presacral length. Both have a relatively small scapula. And a long list of minor traits. Shifting Potamogale to Tenrec adds 30 steps to the LRT.

Figure 2. Scutisorex (below) and Crocidura (above) are extant shrews.

Figure 2. Scutisorex (below) and Crocidura (above) are extant shrews.

Based on the shape of the more plesiomorphic dentition
Potamogale (Fig. 1) is the more primitive taxon compared to Scutisorex (Fig. 2). Neither is very much like Tenrec (Fig. 3).

Figure 3. Tenrec skeleton

Figure 3. Tenrec skeleton, not much in common with Potamogale (Fig. 1). 

 

References
Du Chaillu P 1860. Descriptions of mammals from equatorial Africa. Proceedings of the Boston Society of Natural History, 7, 358–369.
Nicoll M 1985. The biology of the giant otter shrew *Potamogale velox*. National Geographic Society Research Reports, 21: 331-337.

wiki/Giant_otter_shrew

Ontogeny and gender dimorphism in pterosaurs – SVP abstract 2016

Unfortunately,
and apparently, this is yet another study (Anderson and O’Keefe 2016) with a priori species assignations prior to a robust phylogenetic analysis and the creation of precise reconstructions. I hope I’m wrong, but no mention of phylogenetic analysis appears in the abstract. Nor do they mention creating reconstructions. Bennett (1993ab, 1995, 1996a, 2001ab, 2006, 2007) failed several times in similar fashion (with statistical analyses) to shed light on the twin issues of pterosaur ontogeny and dimorphism, coming to the wrong conclusions every time, based on results recovered by creating reconstructions and analyses. Further thoughts follow the abstract.

From the Anderson and O’Keefe abstract:
“The relationships of pterosaurs have been previously inferred from observed traits, depositional environments, and phylogenetic associations. A great deal of research has begun to analyze pterosaur ontogeny, mass estimates, wing dynamics, and sexual dimorphism in the last two decades. The latter has received the least attention because of the large data set required for statistical analyses. Analyzing pterosaurs using osteological measurements will reveal different aspects of size and shape variation in Pterosauria (in place of character states) and sexual dimorphism when present. Some of these variations, not easily recognized visually, will be observed using multivariate allometry methods including Principle Component Analysis (PCA) and bivariate regression analysis. Using PCA to variance analysis has better visualized ontogeny and sexual dimorphism among Pterodactylus antiquus, and Aurorazhdarcho micronyx. Each of the 24 (P. antiquus) and 15 (A. micronyx) specimens had 14 length measurements used to assess isometric and allometric growth. Results for P. antiquus analyses show modular isometric growth in the 4th metacarpal, phalanges I–II, and the femur. Bivariate plots of the ln-geometric mean vs ln-lengths correlate with the PCA showing graphically the relationship between P. antiquus and A. micronyx which are argued here to be sexually dimorphic and conspecific. Wing schematic reconstructions of all 39 specimens were done to calculate individual surface areas and scaled to show relative intraspecific wing shape and size. Finally, Pteranodon, previously identified having with sexually dimorphic groups, was compared with ln-4th metacarpal vs ln-femur data, bivariately, revealing similarities between the two groups (P. antiquus and A. micronyx = group 1; Pteranodon = group 2) in terms of a sexual dimorphic presence within the data sets.”

The Pterodactylus lineage and mislabeled specimens formerly attributed to this "wastebasket" genus

Figure 3. Click to enlarge. The Pterodactylus lineage and mislabeled specimens formerly attributed to this “wastebasket” genus

If these two workers actually had 24 P. antiquus specimens to work with,
then it was only because the labels told them so. Or they came across a cache on a slab of matrix I’m not aware of. Pterodactylus has been a wastebasket taxon for a long time (Fig.1) that, apparently the authors didn’t bother to segregate with analysis. Anderson and O’Keefe do not indicate they arrived at a large clade of P. antiquus specimens after phylogenetic analysis. Having done so, I can tell you that no other tested Pterodactylus is  identical to the holotype and no two adult pterosaurs I’ve tested are alike, even among RhamphorhynchusGermanodactylus and Pteranodon. The differences I’ve scored are individual to phylogenetic and they create cladograms that illuminate interrelationships, not sexual dimorphism or ontogeny. There are sequences of smaller species and larger ones. These can appear to be two genders, but that is a false result.

Embryo to juvenile pterosaurs
are isometrically miniaturized versions of their parents as the evidence shows time and again across the pterosaur clade. These facts have been known for over five years and it’s unfortunate that old traditions continue like this unfettered and untested under phylogenetic analysis… or so it seems… I could be wrong having not seen the presentation.

References
Anderson EC and O’Keefe FR 2016. Analyzing pterosaur ontogeny and sexual dimorphism with multivariate allometery. Abstracts from the 2016 meeting of the Society of Vertebrate Paleontology.
Bennett SC 1993a. The ontogeny of Pteranodon and other pterosaurs. Paleobiology 19, 92–106.
Bennett SC 1993b. Year classes of pterosaurs from the Solnhofen limestone of southern Germany. Journal of Vertebrate Paleontology. 13, 26A.
Bennett SC 1995. A statistical study of Rhamphorhynchus from the Solnhofen limestone of Germany: year classes of a single large species. Journal of Paleontology 69, 569–580.
Bennett SC 1996a. Year-classes of pterosaurs from the Solnhofen limestones of Germany: taxonomic and systematic implications. Journal of Vertebrate Paleontology 16:432–444.
Bennett SC 2001a, b. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260:1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260:113–153.
Bennett SC 2006. Juvenile specimens of the pterosaur Germanodactylus cristatus, with a review of the genus. Journal of Vertebrate Paleontology 26:872–878.
Bennett SC 2007. A review of the pterosaur Ctenochasma: taxonomy and ontogeny. Neues Jahrbuch fur Geologie und Paläontologie, Abhandlungen 245:23–31.