New pterosaur hatchling video from Dr. Witton misinforms

A new video
from Dr. M. Witton looks at the possibility of gliding in hatchling pterosaurs. Unfortunately it is full of misinformation.

Distinct from what Dr. Witton is telling us,
pterosaur hatchling and juvenile proportions are not much different than their 8x larger adult forms. See link below and this growth series image: https://pterosaurheresies.wordpress.com/2015/12/15/pterodaustro-isometric-growth-series/

From the hatchling Pterodaustro image,
Dr. Witton has omitted the skull and neck, but it is present in the egg (it has to be!) and is nearly identical to that of the adult. We looked at a second embryo earlier here (Fig. 2), and for the first embryo see:  http://reptileevolution.com/pterodaustro-embryo.htm for details.

Figure 2. Rough reconstruction using color tracings. Note the elongate jaws and small eye, documenting isometric growth in this pterosaur, as in all others where this can be seen.

Relatively large hatchlings
were able to take flight shortly after hatching. True. The eggs were carried within the mother until ready to hatch, as in many lepidosaurs. The eggshell membrane is also lepidosaurian.

In direct contrast,
the fly-sized hatchllngs of tiny pterosaurs had to grow to a size at which they could leave their damp leaf litter environs, or suffer from desiccation based on their surface-to-volume ratio, as in the tiniest living lizards.  See: https://pterosaurheresies.wordpress.com/2011/08/11/the-tiniest-pterosaur-no-6/

Figure 3. Two of the smallest pterosaurs that both have a large sternal complex. BMNH42736 and B St 1967 I 276.

Gliding is not an option
for baby pterosaurs hatching on the ground. Pterosaurs and their ancestors were flapping before they could fly. Gliding is an ability acquired later in large derived taxa, the same as in birds.

FIgure 4. Dimorphodon take off (with the new small tail).

The quadrupedal launch
shown in several illustrations is not only bogus, but dangerous and inefficient for the pterosaur. Much better to use the giant flapping wing for thrust from the first moment of take-off. For details: https://pterosaurheresies.wordpress.com/2011/07/20/seven-problems-with-the-pterosaur-wing-launch-hypothesis/

Figure 5. Nemicolopterus. This tiny taxon is close to Sinopterus, but closer to Shenzhoupterous. 

Dr. Witton discusses a Sinopterus dongi hatchling.
He is considering tiny adult Nemicolopterus (Fig. 5) a hatchling. The Nemicolopterus specimen has traits distinct from Sinopterus and nests separately in a cladogram closer to Shenzhoupterus, whereas all other adult/hatchling pairs nest together in a pterosaur cladogram. See: http://reptileevolution.com/nemicolopterus.htm

For all future and present paleontologists reading this blog.

It is vitally important that you back up your hypotheses with evidence. Don’t cherry-pick or cherry-delete data to fit your notions or fool an audience.

Pterodaustro isometric growth series

Tradtional paleontologists think pterosaur babies had a cute short rostrum that became longer with maturity and a large orbit that became smaller with maturity (Fig. 1). This is a growth pattern seen in the more familiar birds, crocs and mammals.

Figure 1. Pterodaustro embryo as falsely imagined in Witton 2013. The actual embryo had a small cranium, small eyes and a very long rostrum.

Unfortunately
these paleontologists ignore the fossil evidence (Figs 2, 3). These are the data deniers. They see things their own way, no matter what the evidence is. The data from several pterosaur growth series indicates that hatchlings had adult proportions in the skull and post-crania. We’ve seen that earlier with Zhejiangopterus (Fig. 2), Tapejara, Pteranodon, Rhamphorhynchus and others. Still traditional paleontologists ignore this evidence as they continue to insist that small short rostrum pterosaurs are babies of larger long rostrum pterosaurs.

Figure 2 Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

As readers know,
several pterosaur clades went through a phase of phylogenetic miniaturization, then these small pterosaurs became ancestors for larger clades. Pterosaurs are lepidosaurs and they grow like lepidosaurs do, not like archosaurs do.

Today we’ll look at
the growth series of Pterodaustro (Fig. 1), previously known to yours truly only from adults and embryos. Today we can fill the gaps with some juveniles.

This blog post is meant to help traditional paleontologists get out of their funk.

A recent paper
on the braincase of odd South American Early Cretaceous pterosaur Pterodaustro (Codorniú et al. 2015) pictured three relatively complete skulls from a nesting site (Fig. 1). I scaled the images according to the scale bars then added other available specimens.

Figure 1. Pterodaustro skulls demonstrating an isometric growth series. One juvenile is scaled to the adult length. One adult is scaled to the embryo skull length. There is no short rostrum and large orbit in the younger specimens. If you can see differences in juvenile skulls vs. adult skulls, please let me know. All these specimens come from the same bone bed.

You can’t tell which skulls are adults or juveniles
without scale bars and/or comparable specimens. As we established earlier, embryos are generally one-eighth (12.5%) the size of the adult. Pterodaustro follows this pattern precisely.  We have adults and 1/8 size embryos and several juveniles of intermediate size.

No DGS was employed in this study.

If you know any traditional paleontologists, 
remind them that the data indicates that pterosaurs matured isometrically, like other  lepidosaurs. Those small, short rostrum specimens, principally from the Late Jurassic Solnhofen Formation, are small adults, transitional from larger ancestors to larger descendants. Tiny pterosaurs experiencing phylogenetic miniaturization(as in birds, mammals, crocs, turtles, basal reptiles, and many other clades) that helped their lineage survive while larger forms perished, Sadly, no tiny pterosaurs are known from the Late Cretaceous when they all became extinct.

References
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.
Codorniú L, Paulina-Carabajal A and Gianechini FA 2015. Braincase anatomy of Pterodaustro guinazui, pterodactyloid pterosaur from the Lower Cretaceous of Argentina. Journal of Vertebrate Paleontology, DOI:10.1080/02724634.2015.1031340

More tiny birds and tiny pterosaurs

Earlier we took a peek at a few tiny birds and pterosaurs. Here (Fig. 1) are several more.

Traditional paleontologists
insist that these tiny pterosaurs were babies of larger forms that looked different, (Bennett 1991, 1992, 1994, 1995, 1996, 2001, 2006, 2007, 2012, 2014) ignoring or not aware of the fact that we know pterosaur embryos and juveniles were virtually identical to their adult counterparts (Fig. 2). Bennett (2006) matched two tiny short-snouted pterosaurs (JME SoS 4593 and SoS 4006 (formerly  PTHE No. 1957 52),  to Germanodactylus, but they don’t nest together in the large pterosaur tree.

Figure 1. Tiny pterosaurs and tiny birds to scale showing that tiny pterosaurs were generally about the size of the tiny Early Cretaceous bird. I have, for over a decade, promoted the fact that these tiny pterosaurs were adults, the size of modern hummingbirds and wrens.

One of the most disappointing aspects of modern paleontology
is the refusal of modern pterosaur workers to include in their analyses the small and tiny pterosaurs. They were all the size of living hummingbirds and wrens. Many were similar in size to extinct Early Cretaceous birds (Fig. 1). Those workers don’t want to add these taxa to their lists on the false supposition that the tiny pterosaurs are babies of, so far unknown adults. Note Bennett’s long body of work (see below) indicated otherwise, but never with phylogenetic analysis.

Phylogenetic analysis (Peters 2007) reveals these tiny pterosaurs are adults or can be scored as adults. They are surrounded by adults and they often form transitional taxa in the evolutionary process of phylogenetic miniaturization between larger long-tailed pterosaurs and larger short-tailed pterosaurs.

Figure 2. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen. This is evidence that juveniles were virtually identical to adults, except in size.

More importantly,
earlier we discussed several examples of juvenile pterosaurs morphologically matching adults here, here and here. So young pterosaurs have been shown to match their adult counterparts. They don’t transform like young mammals and dinosaurs do. They were ready to fly upon hatching IF they were the minimum size to avoid desiccation, as discussed earlier here.

The most interesting aspect
to the whole tiny pterosaur story is how small their smallest hatchlings would be. We looked at that earlier here.

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 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 1996. Year-classes of pterosaurs from the Solnhofen limestones of Germany: taxonomic and systematic implications. Journal of Vertebrate Paleontology 16:432–444.
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
Bennett SC 2006. Juvenile specimens of the pterosaur Germanodactylus cristatus, with a revision of the genus. Journal of Vertebrate Paleontology 26(4): 872–878.
Bennett SC 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Bennett  SC (2012) [2013] New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift (advance online publication) doi: 10.1007/s12542-012-0159-8
http://link.springer.com/article/10.1007/s12542-012-0159-8
Bennett SC 2014. A new specimen of the pterosaur Scaphognathus crassirostris, with comments on constraint of cervical vertebrae number in pterosaurs. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 271(3): 327-348.
Peters D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27

 

An Egg for Quetzalcoatlus

After the discovery of at least 4 and maybe 5 pterosaur eggs, now we know their pattern. Based on pelvic diameter, we know the maximum diameter of an egg. The length and shape varies: longer for long-snouted taxa. Hatchlings were 1/8 the size of adults, based on egg size and the example of the embryo Pterodaustro. Hatchlings were virtual copies of adults (contra traditional thinking).

A Hypothetical Egg for the Largest of all Pterosaurs 
Quetzalcoatlus, the largest pterosaur, would have laid the largest pterosaur egg. Figure 1 portrays the Q. sp. smaller version and a 2.3x larger hypothetical Q. northropi pelvis associated with a 0.12x hatchling tucked into an egg shape. It’s no surprise that the hypothetical diameter of an egg that would contain the hatchling exactly matches the pelvic opening. The egg of Quetzalcoatlus would have been elongated to contain the elongated skeletal elements. Within the pelvis, such an egg would have extended anterior to the prepubes.

Figure 1. Quetzalcoatlus northropi and Q. sp. to the same scale alongside hypothetical eggs and hatchlings one-eighth as tall as the adult in each case. Q. northropi was 2.3x as large as the smaller, more complete, unnamed species. This image is to the same scale as the ostrich in Figure 2.

Compared to the Ostrich
The largest living bird, the ostrich, provides some comparison. The ostrich is the largest bird and it produces the largest egg, but that egg is the smallest relative to adult size. Figures 1 and 2 are to the same scale. The large Quetzalcoatlus egg would have been smaller in diameter than the ostrich egg, but 2.5x longer. Longer eggs are possible when the shell is extremely thin and relatively pliable, like those of snakes and lizards.

Figure 2. The ostrich is the largest bird and it produces the largest egg, but it is the smallest egg relative to the adult size.

Hypothetical Details of the Quetzalcoatlus Embryo
With the examples of other pterosaur eggs, we should expect the proportions of the Quetzalcoatlus hatchling to match those of the parent. In order to cram in the long beak, long, stiff neck and elongated metacarpals, the containing egg has to be long. As in other reptiles, the jaws would have been tipped down, pressed against the ventral neck. The eyes would have been relatively no larger than in the adult. The jaws would have been no shorter than in the adult. The legs would have been tucked up against the torso and the feet would have been hyperflexed.

Figure 3. Quetzalcoatlus embryo and egg. The elongated shape and soft, thin shell were needed to encompass the elongated beak, neck and metacarpals.

The Benefit of Being a Lizard
As lizards, pterosaurs could have retained their eggs within the mother until embryonic development was complete. Perhaps only one was produced at a time. A hatchling would have been large enough and well-developed enough (following the pattern of several smaller pterosaur embryos) to be able to fly.

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
Kellner AWA and Langston W 1996. Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from late Cretaceous sediments of Big Bend National Park, Texas. – Journal of Vertebrate Paleontology 16: 222–231.
Lawson DA 1975. Pterosaur from the latest Cretaceous of West Texas: discovery of the largest flying creature. Science 187: 947-948.

wiki/Quetzalcoatlus
Tetrapod Zoology blog; Why-azhdarchids-were-giant-storks