“Renestosaurus” rossii and the DGS Method

Updated with a new reconstruction July 2, 2014.

Bizzarini and Muscio (1995) and Bizzarini, Muscio and Rossi (1995) introduced MFSN 19235 (Fig. 1) as a new species (L. rossii) of Langobardisaurus, the long-necked tritosaur (then wrongly considered a protorosaur). The fossil is represented by part and counterpart of more than a dozen broken pieces. Most of the skull pieces are missing and replaced with putty. Other bones are decayed. Bizzarini, Muscio and Rossi (1995)  considered the broken mandible a series of elongated neck vertebrae with the skull curled back.

MFSN 19235, Renestosaurus

Figure 1. Click to enlarge. This image updates an earlier one. MFSN 19235, once considered Langobardisaurus rossii and here renamed Renestosaurus rossii. The torso was actually flatter than shown here with ribs transverse as in Dalinghosaurus (fig. 3). Note that the long ventral torso bone tentatively identified as the interclavicle by Renesto and Dalla Vecchia (2007) is the left humerus. The rest of the left arm extends dorsally and is disarticulated. Higher resolution enabled better identification of elements. The nesting on the large reptile tree did not change, between Gephyrosaurus and basal squamates.

This post has been updated with the reception of an image of higher resolution.

 

Figure 2. Langobardisaurus(?) rossii (MFSN 19235) reconstructed. Here it nests between basal sphenodontids and basal tritosaurs + squamates.

Figure 2. Langobardisaurus(?) rossii (MFSN 19235) reconstructed. Here it nests between basal sphenodontids and basal tritosaurs + squamates.

 

Renesto and Dalla Vecchia (2007) redescribed the skeleton, concluding that it did not exhibit any “protorosaurian” characters, but all evidence supported attribution to the Lepidosauromorpha with some skull traits possibly supporting a sphenodontian affinity. They re-identified the former neck vertebrae as dentary fragments and noted the actual cervicals were short and small. They found the pisiform, which suggested inclusion within the Lepidosauromorpha. Renesto and Dalla Vecchia (2007) noted what remains of the skull suggested affinity with the Sphenodontia, but preservation was “too poor to allow a firm assignment to this group.”

Homoeosaurus

Figure 2. Homeosaurus, a sister to Dalinghosaurus and Renestosaurus at the base of the Squamates, not far from the Sphenodontia.

Here (Fig. 1), using DGS (digital graphic segregation), reconstruction and phylogenetic analysis permits a firm assignment of MFSN 19235 to the base of the small clade that also includes Homoeosaurus (Fig. 2) and Dalinghosaurus (Fig. 3), both nesting at the base of the Squamates and derived from a sister to Gephyrosaurus. MFSN 19235 may someday be considered a species of Homoeosaurus, but let’s call it Renestosaurus rossii until someone comes along and writes a paper on this clade. This species is a sister to Marmoretta + Megachirella and  Gephyrosaurus at the base of the Sphenodontia, somewhat supporting the tentative conclusions of Renesto and Dalla Vecchia (2007).

Reconstruction of Dalinghosaurus

Figure 3. Reconstruction of Dalinghosaurus, note the larger girdles and more asymmetrical manus and pes.

Note that the long ventral torso bone tentatively identified as the interclavicle by Renesto and Dalla Vecchia (2007) is the other femur extending anteriorly. The other tibia, fibula and pes are mixed in with the anterior dorsal ribs. A higher resolution image should resolve these similar elements better than done here (Fig. 1). A smaller interclavicle matching a smaller pectoral girdle is identified here (Fig. 1).

The DGS method permitted identification of nearly every post-cranial bone. Phylogenetic analysis nested Renestosaurus with the homoeosaur clade. Traits are indeed similar.

Like its sisters the tarsus is no co-ossified. The torso is wide. The scapula is anteriorly embayed.

Unlike its sisters the pectoral and pelvic girdles were relatively small. Metacarpal 2 was longer than the others. The manus and pes were relatively more symmetrical.

To those looking for an example of the DGS method, this is one. All challenges are accepted. If you find something wrong, let’s fix it. So far,  not getting too many brave enough to step forward, but lots of bitchin’ as expected.

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
Bizzarini F and Muscio G 1995. Un nuovo rettile (Reptilia, Prolacertiformes) del Norico di Preone (Udine, Italia Nordorientale). Nota Prelimininare. Gortania – Atti Mus. Friulli. Sti. Nat., 16 (1994): 67-76, Udine.
Bizzarini F, Muscio G and Rossi IA 1995. Un nuovo rettile fossile Langobardisaurus? rossiin. sp. Prolacertiformes (Reptilia) della val Preone (UD), Prealpi Carniche Italine. 1-35 Grafiche Tipo, Catelgomberto.
Renesto S and Dalla Vecchia F 2007. A revision of Langobardisaurus rossii Bizzarini and Muscio, 1995, from the Late Triassic of Friuli (Italy)*

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One thought on ““Renestosaurus” rossii and the DGS Method

  1. Steps 4 and 6 confuse me. When you say “run through analysis” I am assuming you mean a phylogenetic analysis. Is this correct? What do you mean “make corrections” in step 6. Corrections to the drawing? To your character states? Both? Something else?

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