Recumbirostra

Recumbirostra is a clade of tetrapods which lived during the Carboniferous and Permian periods. They are thought to have had a fossorial (burrowing) lifestyle and the group includes both short-bodied and long-bodied snake-like forms.^[1][2] At least one species, the long-bodied molgophid Nagini mazonense, lost its forelimbs entirely.^[3] Recumbirostra includes the families Pantylidae, Gymnarthridae, Ostodolepidae, Rhynchonkidae and Brachystelechidae, with additional families such as Microbrachidae and Molgophidae being included by some authors.^[4][5] Brachystelechidae and Molgophidae have also been grouped together in the suggested clade Chthonosauria.^[6]

Recumbirostra Temporal range: Late Carboniferous - Early Permian, 323.2–293.52 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Life restoration of the rhynchonkid Rhynchonkos
Life restoration of Batropetes, a brachystelechid
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	†Microsauria
Clade:	†Recumbirostra Anderson, 2007
Subgroups
see text

Recumbirostra was erected as a clade in 2007 to include many of the taxa traditionally grouped in "Microsauria", which has since been shown to be a paraphyletic or polyphyletic grouping.^[7][8][9] Like other "microsaurs", the recumbirostrans have traditionally been considered to be members of the subclass Lepospondyli; however, many phylogenetic analyses conducted since the 2010s have recovered recumbirostrans as basal sauropsid (reptilian) amniotes instead.^{[10][7][5][3][11]} However, the placement of recumbirostrans as reptiles has been challenged by other authors, who have recovered them as stem-amniotes instead, and contended that the shared characters between recumbirostrans and reptiles are convergent,^[12] or the result of incorrect character encoding.^[13] Not all phylogenetic analyses recognize Recumbirostra as a valid grouping. An alternative clade called Tuditanomorpha is occasionally supported and includes many of the same taxa.^[14] Furthermore, the taxa that are often considered to be recumbirostrans have been found among amphibians (and not as a distinct clade) in some analyses.^[15]

Classification

Taxonomy

• Altenglanerpeton
• Sparodus
• Steenerpeton?
• Trihecaton?
• Hapsidopareiidae
• Microbrachidae?
• Pantylidae
• Odonterpetidae
  • Odonterpeton
  • Joermungandr
• Chthonosauria
  • Brachystelechidae
  • Lysorophia?
• Nastrondormes^[16]
  • Gymnarthridae
  • Rhynchonkidae / Goniorhynchidae
    • Aletrimyti
    • Dvellecanus
    • Rhynchonkos
  • Ostodolepidae

Phylogeny

Below is a cladogram showing the phylogenetic relationships of recumbirostrans from Glienke (2012):^[4]

Recumbirostra	Microbrachidae Microbrachis Pantylidae Pantylus Stegotretus Sparodus Gymnarthridae Cardiocephalus sternbergi Cardiocephalus peabodyi Euryodus primus Euryodus dalyae Ostodolepidae Pelodosotis Micraroter Goniorhynchidae Rhynchonkos Eocaecilia Tambaroter Altenglanerpeton Brachystelechidae Batropetes Carrolla Quasicaecilia

Gallery

• 
  Skeleton of Joermungandr bolti, showing preserved remains of scales
• 
  Skeleton of the brachystelechid Batropetes
• 
  Skull of the molgophid Brachydectes
• 
  Skull of the ostodolepid Nannaroter