Evolution? Individual Variation? or Both in Pterodactylus?

Today we’ll look at two Pterodactylus specimens that some might consider conspecific. Maybe they are.

Pterodactylus sp. Museum number and scale unknown. From the Houston Museum Archaeopteryx Exhibit 2010.

Figure 1. Pterodactylus sp. Museum number and scale unknown. From the Houston Museum Archaeopteryx Exhibit 2010. In situ fossil plate and counterplate shown below. The only disarticulated parts are the terminal tail vertebrae which are reassembled here. Coracoid length is estimated.

A comparison is worthwhile
I traced and reconstructed a Pterodactylus (Fig. 1) featured in the Houston Museum Archaeopteryx exhibit from 2010. I do not know the museum number or scale (If you can help with this, please do!). The closest specimen I have studied is Pterodactylus scolopaciceps (Broili 1938, BSP 1937 I 18, No. 21 in the Wellnhofer 1970 catalog). Here the similarities are obvious. There are a few differences, but do these represent individual variation, evolution from one species to another, or both?

Pterodactylus scolopaciceps.

Figure 2. Pterodactylus scolopaciceps, BSP 1937 I 18, No. 21 in the Wellnhofer 1970 catalog.

In the unnumbered specimen the teeth are smaller.

The sternum is slightly longer.

The anterior dorsal ribs are shorter.

The deltopectoral crest is rounder.

The anterior ilium is longer and the posterior ilium is shorter.

Metatarsal 3 is slightly longer.

Pedal 2.2 is slightly longer.

Pedal digits 2-4 are closer to lining up.

Usually we like to see larger steps that can be better quantified.
Most of the time ptero-paleontologists ignore specimens that don’t show much variation, but this is how evolution proceeds, small steps at a time.  Here I thought it might be worthwhile to see the very small variations that, over time, can become larger variations creating distinct species.

The gamut of Pterodactylus morphologies can be seen here (Fig. 3). The Houston specimen and No. 21 appear in the middle of the lineage.

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

The Houston exhibit Pterodactylus specimen is pretty much standard for the clade. It is preserved in extraordinary articulation in part and counterpart (plate and counterplate) with slight impressions of soft tissue (Fig. 5). None of these bring any surprises. or new insight.

Pterodactylus from the Houston Museum Archaeopteryx exhibit 2010, plate.

Figure 4. Pterodactylus from the Houston Museum Archaeopteryx exhibit 2010, plate.

Pterodactylus from the Houston Museum Archaeopteryx exhibit 2010, counterplate.

Figure 4. Pterodactylus from the Houston Museum Archaeopteryx exhibit 2010, counterplate. These two images were merged onto a single Photoshop file to create the tracing (Fig. 5) and reconstruction (Fig. 1).

Pterodactylus from the Houston Museum Archaeopteryx Exhibit 2010 with color overlays for soft tissue preservation.

Figure 5. Pterodactylus from the Houston Museum Archaeopteryx Exhibit 2010 with color overlays for soft tissue preservation. This is a near perfect preservation in complete articulation.

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
Broili F 1938. Beobachtungen an Pterodactylus. Sitz-Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-naturalischenAbteilung: 139–154.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

wiki/Pterodactylus

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