The LH 20523 specimen of Scandensia is really Tijubina

Two lizards were described in 2011.
Bolet and Evans (2011) described what they thought was ‘new material’ of Scandensia (LH 20523), but it had a very long stiff tail and tiny rib osteoderms. This specimen is only known from the posterior half (Fig. 1). Simões (2011) redescribed the complete Tijubina, which also had a very long stiff tail and tiny rib osteoderms. Both are from the Early Cretaceous, the former from Spain, the latter from Brazil.

The large reptile tree nested the LH 20523 specimen with Tijubina, in the middle of the Tritosauria, several nodes away from Scandensia. The holotype of Scandensia nests between basal rhynchocelphalians and basal squamates + tritosaurs. It doesn’t have a long stiff tail or dorsal osteoderms. Distinct from the LH 20523 specimen, Scandensia has a lumbar region of very short ribs.

Figure 1. Tijubina and Scandensia holotypes. Scandensia is a much larger genus. The tail is not well preserved and could be longer in Scandensia. Note the lumbar area in Scandensia not present in Tijubina. Also note the great size of metatarsal 4 in Tijubina, not present in Scandensia.

Figure 1. Tijubina and Scandensia holotypes. Scandensia is a much larger genus. The tail is not well preserved and could be longer in Scandensia. Note the lumbar area in Scandensia not present in Tijubina. Also note the great size of metatarsal 4 in Tijubina, not present in Scandensia.

The LH 20523 specimen has a regenerated tail with cartilaginous growth. The authors estimate the tail was 3x the the snout vent length, which they note contrasts with the holotype of Scandensia, which has subequal tail and snout-vent lengths. This is the first clue that these two are not the same taxon. But then, they reasoned, the Scandensia tail may have been incompletely preserved or regenerating.

The LH 25023 specimen that Bolet and Evans (2011) referred to Scandensia, but nests here with Tijubina.

Figure 2 The LH 25023 specimen that Bolet and Evans (2011) referred to Scandensia, but nests here with Tijubina.

Bolet and Evans (2011) were surprised to see osteoderms around the rib cage because the holotype of Scandensia does not have these. This is the second clue.

The very robust fourth metatarsal is a trait shared with Tijubina, not with Scandensia, a third clue.

Figure 3. Ankles of the LH 25303 specimen. Here Bolet and Evans see a single astragalocalcaneum (in yellow on the drawing) but the photo does not  support a single proximal ankle bone.

Figure 3. Ankles of the LH 20523 specimen. Here Bolet and Evans see a single astragalocalcaneum (in yellow on the drawing, and present in all squamates) but the photo does not support a single proximal ankle bone. Rather a split appears between the astragalus and calcaneum, as in all tritosaurs.

Bolet and Evans report a single astragalocalcaneum, as in Scandensia, but the photo of the LH 20523 specimen shows a split between the proximal ankle bones and the shape is different than shown. Was this wishful thinking? or more precise observation. No tritiosaurs have a fused proximal tarsus, so this would be an autapomorphy if true.

Were Bolet and Evans aware of Tijubina?
I don’t think so. It is not mentioned in their paper. A query to both authors goes unanswered at present.

References
Bolet A and Evans SE 2011. New material on the enigmatic Scandensia, an Early Cretaceous lizard from the Iberian Peninsula. Special Papers in Palaeontology 86:99-108.
Bonfim Júnior DC and Marques RB 1997. Um novo lagarto do Cretáceo do Brazil (Lepidosauria, Squamata, Lacertilia – Formação Santana, Aptiano da Bacia do Araripe. Anuário do Instituto do Geociencias 20:233-240
Bonfim-Júnior F de C and Rocha-Barbosa O 2006. A Paleoautoecologia de Tijubina pontei Bonfim-Júnior & Marques, 1997 (Lepidosauria, Squamata Basal da Formação Santana, Aptiano da Bacia do Araripe, Cretáceo Inferior do Nordeste do Brasil). Anuário do Instituto de Geociências – UFRJ ISSN 0101-9759 Vol. 29 – 2 / 2006 p. 54-65.
Evans SE and Barbadillo LJ 1998. An unusual lizard (Reptilia: Squamata) from the Early Cretaceous of Las Hoyas, Spain. Zoological Journal of the Linnean Society 124:235-265.
Simões TR 2012. Redescription of Tijubina pontei, an early cretaceous lizard (Reptilia; Squamata) from the crato formation of Brazil. An Acad Bras Cienc. Feb 2, 2012. pii: S0001-37652012005000001. [Epub ahead of print].

 

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