Hauffiosaurus: convergent with later plesiosaurs

Updated March 28, 2019
with a new old engraving of Anningasaura.

Two misfit plesiosaurs nest together in the LRT
Earlier we looked at Anningsaura (Fig. 6)Vincent and Benson (2012) reported, “In general morphology, NHMUK OR49202 does not resemble any known plesiosaurian taxon.”

Figure 2. The sisters of Anningsaura, Simosaurus and Pistosaurus.

Figure 1. The sisters of Anningsaura, Simosaurus and Pistosaurus. Until today, these provided the only clues as to the post-crania of Anningsaura, of which only the first eight cervicals are known.

Anningasaura 
(originally Plesiosaurus macrocephalus, Lydekker 1889; NHMUK OR49202) represents a completely ‘new’ branch of the plesiosauria in which the orbits virtually cannot be seen in dorsal view and the jugals bend down posteriorly to produce an angled temporal arch (Fig. 1). Moreover the premaxillae were thought to not contact the frontals and the nasals were absent. Benson et al. (2012) created a phylogenetic analysis that nested Anningsasaura at the base of the pliosaur/plesiosaur split with Bobosaurus as the outgroup.

Figure 1. Hauffiosaurus from Vincent 2011 with colors and reconstructions added.

Figure 2. Hauffiosaurus from Vincent 2011 with colors and reconstructions added.

Hauffiosaurus zanoni 
(O’Keefe 2001; Vincent 2011; Early Jurassic; 3.4m long; uncatalogued Hauff museum) is another plesiosaur that, according to Vincent 2011, “does not resemble any known plesiosaurian taxon.” This genus was considered a basal pliosauroid. Here (Fig. 3) the large reptile tree (LRT, 1392 taxa) nests between Anningsaura and Pistosaurus. Benson et al 2012 nested Hauffiosaurus one or two nodes apart from Anningsaura. No taxa in those nodes is currently in the LRT. So the LRT is a close match!

As you might imagine,
the characters in the LRT are not the same as those found in Benson et al. 2012, yet the tree topologies, so much as they can be compared, are nearly identical. This was done without first-hand access to the fossils. So, this methodology works.

Figure 3. Subset of the LRT. Here the clade Eosauropterygia nests Anningsaura with Hauffiosaurus.

Figure 3. Subset of the LRT. Here the clade Eosauropterygia nests Anningsaura with Hauffiosaurus. This nesting demonstrates an early convergence with later pliosaurids.

The skull of Hauffiosaurus is exposed in palatal view
(Fig. 4) and as such gives clear data on the often hidden palatal elements. Overlooked by Vincent 2011, the premaxilla extends to the internal naris, as in other taxa (Fig. 5), like Pliosaurus, also an overlooked connection.

Figure 4. Hauffiosaurus skull in palatal view from Vincent 2011, colors added. Overlooked by Vincent, the premaxilla (yellow) contacts the internal naris

Figure 4. Hauffiosaurus skull in palatal view from Vincent 2011, colors added. Overlooked by Vincent, the premaxilla (yellow) contacts the internal naris

DGS is able to document traits
overlooked by those with first-hand access to the fossils themselves (Figs. 4, 5).

Figure 4. Pliosaurus kevani palate, from Benson et al. 2013, also has an overlooked premaxilla-internal naris contact.

Figure 5. Pliosaurus kevani palate, from Benson et al. 2013, also has an overlooked premaxilla-internal naris contact. Red ellipses encircle the internal nares, probably too small for respiration.

Figure 6. Anningasaura colorized from an old engraving. No other aquatic taxon has such bizarrely curved teeth. This taxon is closely related to Hauffiosaurus.

Figure 6. Anningasaura colorized from an old engraving. No other aquatic taxon has such bizarrely curved teeth. This taxon is closely related to Hauffiosaurus, so it provides insight into the lateral view of Hauffiosaurus.

References
Benson RBJ, Evans M, Druckenmiller PS 2012. Lalueza-Fox, Carles. ed. ”High Diversity, Low Disparity and Small Body Size in Plesiosaurs (Reptilia, Sauropterygia) from the Triassic–Jurassic Boundary”. PLoS ONE 7 (3): e31838. doi:10.1371/journal.pone.0031838
Benson RBJ, et al. (6 co-authors) 2013. A giant pliosaurid skull from the Late Jurassic of England. PLoS ONE 8(5): e65989. doi:10.1371/journal.pone.0065989
Dalla Vecchia FM 2006. A new sauropterygian reptile with plesiosaurian affinity from the Late Triassic of Italy. Rivista Italiana di Paleontologia e Stratigrafia 112 (2): 207–225.
O’Keefe RF 2001. A cladistic analysis and taxonomic revision of the Plesiosauria (Reptilia: Sauropterygia). Acta Zoologica Fennica 213:1–63.
Vincent P 2011. A re-examination of Hauffiosaurus zanoni, a pliosauroid from the Toarcian (Early Jurassic) of Germany. Journal of Vertebrate Paleontology 31(2): 340–351.
Vincent P and Benson RBJ 2012. Anningasaura, a basal plesiosaurian (Reptilia, Plesiosauria) from the Lower Jurassic of Lyme Regis, United Kingdom, Journal of Vertebrate Paleontology, 32:5, 1049-1063.

wiki/Anningasaura
wiki/Hauffiosaurus

 

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