Lessemsaurus

Lessemsaurus is an extinct genus of sauropodiform dinosaur belonging to Lessemsauridae.

Lessemsaurus Temporal range: Norian ~228–208.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Reconstructed skeleton
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Family:	†Lessemsauridae
Genus:	†Lessemsaurus Bonaparte 1999
Species:	†L. sauropoides
Binomial name
†Lessemsaurus sauropoides Bonaparte 1999

Naming and description

The type species, L. sauropoides, was formally described by José Fernando Bonaparte in 1999 in honor of Don Lessem, a writer of popular science books. It was found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in La Rioja Province, Argentina.^[1]

It was discovered in strata dating to the Norian stage, around 210 million years ago.^[2][3] It is estimated to have reached 10–12 metres (33–39 ft) long and weighed over 7 metric tons (7.7 short tons), possibly up to 8–10 metric tons (8.8–11.0 short tons), in maximum body mass.^[4][5][6][7]

Classification

Exhibit in Singapore

A cladogram after Pol, Garrido & Cerda, 2011,^[8] illustrates a possible placing of Lessemsaurus and Antetonitrus in Sauropodomorpha:

Sauropodomorpha	Saturnalia Pantydraco Thecodontosaurus Efraasia Ruehleia Plateosaurus Massopoda Riojasaurus Massospondylus Coloradisaurus Lufengosaurus Gyposaurus Yunnanosaurus Anchisauria Anchisaurus Aardonyx Leonerasaurus Melanorosaurus Sauropoda Antetonitrus Lessemsaurus Kotasaurus Vulcanodon Eusauropoda

In 2018, Apaldetti et al. recovered it as part of a clade they named Lessemsauridae, after Lessemsaurus. Their cladogram is reproduced below:^[9]

Sauropodiformes	Mussaurus Aardonyx Sefapanosaurus Melanorosauridae Camelotia Melanorosaurus Sauropoda Lessemsauridae Antetonitrus Ingentia Lessemsaurus Blikanasaurus Gongxianosaurus Pulanesaura Gravisauria

The following cladogram shows the position of Lessemsaurus outside of Sauropoda, according to Oliver W. M. Rauhut and colleagues, 2020:^[10]

Massopoda

Eucnemesaurus Riojasaurus Sarahsaurus Massospondylidae Yunnanosaurus Jingshanosaurus Seitaad Coloradisaurus Glacialisaurus Lufengosaurus Massospondylus Adeopapposaurus Leyesaurus Sauropodiformes Xingxiulong Anchisaurus Leonerasaurus Mussaurus Aardonyx Sefapanosaurus Meroktenos Melanorosaurus Camelotia Lessemsaurus Antetonitrus Ingentia Blikanasaurus Pulanesaura Gongxianosaurus Schleitheimia Isanosaurus Tazoudasaurus Sauropoda