Mousebirds (genus: Urocolius)

Yesterday we looked at the hoopoe (genus: Upupa)
famous for its head crest of elevating feathers. Today we look at its sister, the mousebird (genus: Urocolius) which has a similar feathery crest, but differs in having a short parrot-like beak, a long parrot-like tail and a rare parrot-like reversible toe 4. These nest between toucans + hornbills and barbets + tropicbirds. These birds share a deep maxilla with a relatively elevated jugal (Fig. 1).

Figure 1. Urocolius, the blue-napes mousebird, converges with parrots in having a reversible toe 4, the ability to feed upside-down and having a short, deep, hooked beak...plus that long parrot-like tail!

Figure 1. Urocolius, the blue-napes mousebird, converges with parrots in having a reversible toe 4, the ability to feed upside-down and having a short, deep, hooked beak…plus that long parrot-like tail! The pygostyle is missing from this specimen.

Urocolius macrourus (Bonaparte 1854; 10cm snout-vent length) is the extant blue-naped mousebird, a member of the Coliiformers. Note the deep maxilla compared to the jugal. It nests with the hoopoe in the large reptile tree between hornbills and barbets. An omniovore restricted to sub-Saharan Africa, mousebirds build nests. They are gregarious, acrobatic and scurry through the leaves like rodents. Reversible toe 4 is able to rotate posteriorly, as in the related toucan, Pteroglossus.

References
Bonaparte CL 1854. En Ateneo Italiano. 1854. 2: 313.
wiki/Urocolius
wiki/Mousebird

Guesswork parades as science: the ‘Dawndraco’ debate continues

Kellner 2017 rebutted Martin-Silverstone et al. 2017
who rebutted Kellner 2010 in their taxonomic assessment of a Pteranodon specimen UALVP 24238. Is it congeneric with FHSM VP 339 (GeoternbergiiaP. sternbergi)? Or is the UALVP specimen a distinct genus? Or something else…?

Figure 1. Pteranoodn (Dawndraco) UALVP 24238 in situ, with Martin-Silverstone tracing applied, with mandible moved and missing parts colorized. The putative rostral tip looks more like displaced manus elements.

Figure 1. Pteranoodn (Dawndraco) UALVP 24238 in situ, with Martin-Silverstone tracing applied, with mandible moved and missing parts colorized. The putative rostral tip looks more like displaced manus elements.

Both parties wondered about
gender differences based on pelvis shape. (Both had no clue that the one ‘female’ pelvis they pin their hopes on actually belongs to a giant Nyctosaurus).

Both parties wondered about
maturity at the age of death and used bone fusion as an ontogenetic marker. (Both have no clue that fusion patterns are phylogenetic in pterosaurs because pterosaurs are lepidosaurs and fusion patterns don’t match those of archosaurs, according to Maisano 2002a, b and confirmed by phylogenetic analysis).

Martin-Silverstone et al. dismiss
several observed variations due to postmortem distortion, evidently a favorite excuse of many paleontologists when they have run out of answers that fit their paradigm. (No distortion is found in UALVP 24238).

Name calling, too…
Kellner felt he had to defend being labeled as a ‘splitter’.

Kellner adds one more thought:
“As I have stressed before (Kellner 2010), morphology is crucial for establishing or synonymizing species.” (Very unfortunately both authors do not understand what pterosaurs are: they are fenestrasaur tritosaur lepidosaurs, because they had not performed a phylogenetic analysis in arriving at their conclusions. Only when that happens, THEN establishing and synonymizing species can happen as a result. You just have to read the tree to see who is, or is not, related to who.

Lately everyone in pterosaurs seems to be avoiding
this thing called, “phylogenetic analysis” which, in the large pterosaur tree (LPT, 232 taxa) successfully split and lumped every tested pterosaur specimen, including over a dozen Pteranodon specimens (Fig. 2). It turns out UALVP 24283 (fig. 2, specimen ‘Z’) is not a sister to FHSM VP 339 (Fig. 2, specimen ‘Y’), but both have a common ancestor close to specimen ‘W’ USNM 12167 (Fig. 2, undescribed). Do not accept pterosaur topologies that test only genera and avoid the tiny Solnhofen pterosaurs. You won’t get the big picture and you won’t speak with authority. You’ll floundering in guesswork.

Figure 2. The Tanking-Davis specimen compared to other forms. Specimen w and specimen z appear to be the closest to the Tanking-David specimen. Specimen 'w' = Pteranodon sternbergi? USNM 12167 (undescribed). Specimen 'z' = Pteranodon longiceps? Dawndraco? UALVP 24238. Click to enlarge.

Figure 2.  Click to enlarge. Every reasonably complete Pteranodon skull to scale and in phylogenetic order.

In phylogenetic analysis a big crest
is a derived trait, and yet some small crests and small skulls are derived from big crest ancestors. Only analysis reveals this.

There are no gender differences here.
No two skulls (Fig. 2) are identical except for their crests. And every Pteranodon pelvis is different. The variety here is due to phylogeny, not gender or ontogeny.

Ontogeny is only demonstrated
by the smallest Pteranodon specimens (next to specimen ‘Q’).

Why so much variety in Pteranodon?
Well, there is so much variety in every putative genus in pterosaurs. Add to that, Pteranodon lived for several million years along the long Niobrara Sea that crossed North America from Canada to the Gulf of Mexico… and who knows wherever else. That provides many latitudes for this genus to inhabit and niches to evolve to.

Pterosaur workers,
stop being so lazy! Use specimens for taxa, not a single representative from each genus. That will solve so many taxon exclusion problems, as I can tell you from experience. When you do, let me know what you get. You can safely ignore all previously published topologies that exclude so many taxa. That they are all different teaches us that those all teach us nothing.

If you want my opinion:
Keep all Pteranodon specimens (shown above in Fig. 2) within the genus Pteranodon. Divide them into species. Each one should get it’s own species. Currently ‘Dawndraco‘ nests between several other specimens referred to Pteranodon. That’s how you know ‘Dawndraco‘ really is Pteranodon.

And while you’re at it:
Keep all Rhamphorhynchus specimens (Fig. 3) within the genus Rhamphorhynchus. Divide them into species. Do the same with all Pterodactylus, Dorygnathus, Scaphognathus, etc. genera. Employ more specimens/taxa. Exclude them at your scientific peril.

Figure 3. Bennett 1975 determined that all these Rhamphorhynchus specimens were conspecific and that all differences could be attributed to ontogeny, otherwise known as growth to maturity and old age. Thus only the two largest specimens were adults. O'Sullivan and Martill took the brave step of erecting a new species. The n52 specimen is at the lower right. Click to enlarge.

Figure 3. Bennett 1975 determined that all these Rhamphorhynchus specimens were conspecific and that all differences could be attributed to ontogeny, otherwise known as growth to maturity and old age. Thus only the two largest specimens were adults. O’Sullivan and Martill took the brave step of erecting a new species. The n52 specimen is at the lower right. Click to enlarge.

References
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Bennett SC 2001. 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.
Kellner AWA 2010. Comments on the Pteranodontidae (Pterosauria, Pterodactyloidea)
with the description of two new species. Anais da Academia Brasileira de Ciências 82(4): 1063-1084.
Kellner A 2017.  Rebuttal of Martin-Silverstone et al. 2017, ‘Reassessment of Dawndraco kanzai Kellner 2010 and reassignment of the type specimen to Pteranodon sternbergi Harksen, 1966’Vertebrate Anatomy Morphology Palaeontology 3:81–89.
Maisano JA 2002a. The potential utility of postnatal skeletal developmental patterns in squamate phylogenetics. Journal of Vertebrate Paleontology 22:82A.
Maisano JA 2002b. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
Martin-Silverstone E, Glaser JRN, Acorn JH, Mohr S and Currie PJ 2017. Reassesment of Dawndraco kanzai Kellner, 2010 and reassignment of the type specimen to Pteranodon sternbergi Harksen, 1966.  Vertebrate Anatomy Morphology Palaeontology 3:47-59.
Marsh OC 1876a. Notice of a new sub-order of Pterosauria. American Journal of Science, Series 3, 11:507-509.
Miller HW 1971. A skull of Pteranodon (Longicepia) longiceps Marsh associated with wing and body parts. Kansas Academy of Science, Transactions 74(10):20-33.

http://www.reptileevolution.com/pteranodon-skulls.htm

Parietal crests on lepidosaurs

Yesterday’s post on several iguanids, one of them crested, inspired this post on parietal crests found on lepidosaurs. I wondered how many other reptiles had vertical parietal crests? (This separates ceratopsians and other with horizontal expansions of the parietal.) And how many other lepidosaurs? And how many other squamates?

Figure 1. The parietal crest of various lepidosaurs are compared here. Upper left: Corytophanes. Upper right: Basiliscus. Lower: Nytosaurus (KJ@) and Pteranodon (Jenkins specimen).

Figure 1. The parietal crest of various lepidosaurs are compared here. Upper left: Corytophanes. Upper right: Basiliscus. Lower: Nytosaurus (KJ@) and Pteranodon (Jenkins specimen).

Among squamates
crests are few. Trioceros (Fig. 2) has a vertical parietal crest. Other squamates related to Basiliscus and Corytophanes have similar crests.

Several pterosaur lepidosaurs had vertical crests.
Many were independently created. Others further extended the smaller crests of more primitive ancestors. So far as the data will take us, crests are only phylogenetic in size and shape. We have evidence for maturity level in crest shape and size, after all, it would be very difficult to tuck a long or large parietal crest into an eggshell.

On a side matter,
what sort of elongated egg shape might contain the extremely elongated rostrum of Moganopterus (Fig. 2)?? I’m willing to suspect that this pterosaur, perhaps uniquely, elongated the rostrum during ontogeny. But then Pterodaustro did not do so, so who knows?

The pterosaur Hamipterus might give us a tentative clue as to gender identity in nasal crests, but it’s not a certainty at present.

Figure 2. Parietal crests on other lepidosaurs, including several often unrelated pterosaurs.

Figure 2. Parietal crests on other lepidosaurs, including several often unrelated pterosaurs. The crest of Cosesaurus is soft, unossified and no close relatives have an ossified crest. Not to scale. 

Parietal crests on archosauromorphs
are not impossible to find, but they are rare. You can find parietal crests on certain plesiosaurs, like Pistosaurus, Trinacromerum (Fig. 3) and Brachauchenius. They would have been hidden by jaw muscles in life.

Figure 3. The plesiosaur Trinacromerum has a parietal crest, but it was laterally packed with jaw muscles.

Figure 3. The plesiosaur Trinacromerum has a parietal crest, but it was laterally packed with jaw muscles.

Likewise
on certain ichthyosaurs like Shonisaurus, Cymbospondylus and PhalarodonContectopalatus (Fig. 4). As in the plesiosaurs (above) these crests served as anchors for powerful jaw muscles.

Figure 4. Phalarodon and Contectopalatus are ichthyosaurs with a parietal crest, likewise laterally hidden in vivo with large jaw muscles.

Figure 4. Phalarodon and Contectopalatus are ichthyosaurs with a parietal crest, likewise laterally hidden in vivo with large jaw muscles.

 

The crests on hadrosaurs and certain theropods, including cassowaries, are enlarged nasals. I never thought this would add even a mote of evidence to the pterosaurs are lepidosaurs argument, but it does add one little mote, just as the longest cervicals are found in tanystropheids and azhdarchids. Coincidence? Or a genetic wild card?

Figure 1. Macrochelys (Macroclemys) skull colorized. Most workers label the bone above the curled quadrate as a squamosal, but here it is considered a supratemporal, which has horns in basal turtles.

Figure 5. Macrochelys (Macroclemys) skull colorized. Most workers label the bone above the curled quadrate as a squamosal, but here it is considered a supratemporal, which has horns in basal turtles. This skull shows a minimum of occiput invagination.

Some turtles develop a crest
that is largely created by embayment of the occipital plate of the skull and the narrow portion is chiefly formed by the supra occipital (Fig. 5).

Parietal crest development
in lepidosaurs appears to be largely for species identification and/or secondary sexual selection. In pterosaurs, since they travel at airspeeds in which streamlining and aerodynamics play a large part, crest size and shape must follow those restrictions and head turning would tend to yaw the pterosaur, but not the basilisk.

More crest laminations, this time in a pterosaur

When animals develop crests, it’s rarely just one bone that creates it. We just looked at Lambeosaurus, in which the crest is made of two bones, the premaxilla and nasal (no matter how you divide it). Today we’ll look at Tupuxuara, a crested pterosaur of the Early Cretaceous. It’s interesting to compare how crests grow by watching which bones grow to create them.

Juvenile Tupuxuara

Figure 1. Juvenile Tupuxuara. Colors denote various bones. Note the expansion of the nasal dorsally as in laminates the premaxilla to strengthen it. The premaxilla, frontal and parietal contribute to the cranial portion of the crest.

Several years ago I was lucky enough to photograph a juvenile Tupuxuara skull at the Tucson Gem and Mineral Show. Not only did it have the proportions of an adult (isometric growth in tritosaur lizards), it more clearly differentiated the various bones used to create it. It was also preserved uncrushed and completely worked out of the matrix.

The crest in Tupuxuara is homologous to that in Germanodactylus cristatus, another sharp-jawed pterosaur with a single tooth at the tip. With skull bones often about one millimeter in thickness it helps to laminate one bone upon another for strength, something like a paper sculpture.

Photo of the Tupuxuara juvenile

Figure 2. Photo of the Tupuxuara juvenile. Click to enlarge.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

My what big teeth you have!! Introducing Guidraco

Guidraco venator (Wang et al., 2012) IVPP V17083, ~38 cm skull length, is a new crested ornithocheirid from the Lower Cretaceous of China. It was correctly nested as a sister to Ludodactylus and shared many traits with it and its many toothed South American sisters, like Anhanguera and Cearadactylus, but Guidraco is also a more distant sister to Liaoningopterus from ChinaAn upright crest and enormous anterior teeth set Guidraco apart from the others.

Guidraco in situ

Figure 1. Guidraco in situ from Wang et al. 2012. The extent of the parietal shown here may have something to do with a displaced underlying bone, like a postorbital creating an outline.

Reconstruction
Guidraco was so well preserved that very little reconstruction is necessary. The upper temporal fenestra was large, probably in association with the enlargement of the premaxillary teeth, probably to oppose the pulling vectors brought on by the teeth during prey capture. In ornithocheirid skulls bones often fuse together obliterating sutures. Some of these identifications are based on comparisons to sister taxa.

Guidraco skull reconstructed.

Figure 2. Guidraco skull reconstructed. Not changes with the original in figure 3.

Original Reconstruction
The reconstruction by Wang et al. 2012 includes minor difference from the present reconstruction. Contra the original reconstruction, the premaxilla includes four teeth, including the medial nubbin. The nasal extends further than originally reconstructed, laminated beneath the premaxilla. A stem-like nasal process was present in the antorbital fenestra. Vestigial nares (primary and secondary were present) attended by anterior laminated extensions of the jugal and nasal. The quadratojugal extended up the lateral quadrate, as in other pterosaurs. The upper temporal fenestra and parietal were taller. This matches the shape of the occiput. The postorbital overlapped the squamosal as in other pterosaurs. A postfrontal is present. The sclerotic ring was not so robust.

Original reconstruction by Wang et al. (2012).

Figure 3. Original reconstruction by Wang et al. (2012). Please note several distances.

A Pteranodontoid?
Wang et al. (2012) nested Guidraco and all other ornithocheirids with Pteranodon in a clade called Pteranodontoidea. This odd nesting of toothless with toothy taxa is a product of taxon exclusion. When more taxa are included, as in the large pterosaur tree, ALL the pterosaurs with a pointed rostrum nest together and apart from the toothy ornithocheirids, who find more parsimonious sister nestings with Cycnorhamphus and Scaphognathus, along with several tiny pterosaur intermediates.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Wang X-L, Kellner AWA, Jiang S-X and Cheng X 2012. New toothed flying reptile from Asia: close similarities between early Cretaceous pterosaur faunas from China and Brazil. Naturwissenschaften in press. doi:10.1007/s00114-012-0889-1.

wiki/Ludodactylus
wiki/Guidraco

Mutual Sexual Selection in Pterosaurs and Dinosaurs. Yes!

In a recent paper by Hone, Naish and Cuthill (2011) the authors reviewed the available evidence for the functions of “ornithodiran” [a paraphyletic taxon] cranial crests. They concluded that mutual sexual selection presents a valid hypothesis for their presence and distribution.

Why Did They Feature Pterosaurs?
In their section on pterosaurs Hone, Naish and Cuthill (2011) noted that the majority of pterosaur taxa are known from single specimens (Unwin 2005) “and as a result it cannot generally be determined if crests were present in both sexes.”

Fair enough.

Then they went on to reference Bennett’s work (1992, 1994) promoting sexual dimorphism, but that has been falsified. And it doesn’t support their hypothesis.

They referenced the crestless Darwinopterus with egg (Lu et al. 2011), and reported that it was identical in size to conspecific crested individuals, but actually differences abound and the two are not conspecific. And it doesn’t support their hypothesis.

Ontogeny
Hone, Naish and Cuthill (2011) reference adolescent development of a bony crest in thalassodromids (Martill and Naish 2006), but this example indicates that crests developed long before half adult size had been reached and therefore long before the individual had become interested in sex.

Hone, Naish and Cuthill (2011) referenced strong allometric growth of the crest in Pteranodon (Tomkins et al. 2010), suggesting a role that only becomes relevant after maturity, but that has been falsified as noted earlier. All tritosaurs, including Pteranodon, developed isometrically.

Hone, Naish and Cuthill (2011) reported that the coincident appearance of a structure with maturity is a hallmark of a role in sexual selection. True enough. But the authors failed to show that the appearance of crests in pterosaurs was ontogenetic, rather than phylogenetic. Moreover, they failed to show that both genders sported crests, which was their hypothesis of mutual sexual selection. To support that hypothesiss, I would have reported that every known Dsungaripterus sports the same crest, for instance. Then add in all the Tapejara, Tupuxuara and Thallasodromeus skulls. They could all be male, but the odds are stacked against that.

I Don’t Have any Problem with Mutual Sexual Selection in Pterosaurs
All the present evidence indicates that crests developed in certain pterosaur species only, without regard for age or gender. That indicates mutual sexual selection. So why, then, did Hone, Naish and Cuthill (2011) reference those several cases of sexual dimorphism? It doesn’t make sense given their headline and hypothesis.

Does one wonder how the crestless pterosaurs found each other for mating?
No. Every species had its own identifying marks, whether crest or vane or color or wattle.

Nits and Picks
Hone, Naish and Cuthill (2011, fig. 1) reported that no birds had crests. Actually the hornbill and cassowary have them (not counting roosters and cockatiels).

Nesting pterosaurs with crocodiles and dinosaurs is not valid. Pterosaurs are lizards.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Hone DWE Naish D and Cuthill IC 2011. Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia, DOI: 10.1111/j.1502-3931.2011.00300.x
Lü J, Unwin DM, Deeming DC, Jin X, Liu Y and Ji Q 2011. An egg-adult association, gender, and reproduction in pterosaurs. Science, 331(6015): 321-324. doi:10.1126/science.1197323
Martill DM and Naish D 2006. Cranial crest development in the azhdarchoid pterosaur Tupuxuara, with a review of the genus and tapejarid monophyly. Palaeontology 49, 925-941.
Tomkins JL, Lebas NR, Witton MP, Martill DM and Humphries S 2010. Positive allometry and the prehistory of sexual selection. The American Naturalist 176, 141–148.
Unwin DM 2005. The Pterosaurs: From Deep Time. Pi Press, New York.