Angolatitan

Angolatitan Temporal range: Late Cretaceous, Coniacian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Reconstruction
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Clade:	†Macronaria
Clade:	†Somphospondyli
Genus:	†Angolatitan Mateus et al., 2011
Type species
Angolatitan adamastor Mateus et al., 2011

Angolatitan (meaning "Angolan giant") is a genus of titanosauriform sauropod dinosaur from the Upper Cretaceous. It is also the first non-avian dinosaur discovered in Angola. The genus contains a single species, Angolatitan adamastor, known from a partial right forelimb. Angolatitan was a relict form of its time; it was a Late Cretaceous basal titanosauriform, when more derived titanosaurs were far more common.^[1]

Discovery and naming

Cast of holotypic right humerus, National Museum of Natural History

After the Angolan Civil War ended in 2002, the PaleoAngola project planned the first Angolan palaeontological expeditions since the 1960s. The first of these expeditions started in 2005 to explore Angola's fossil rich upper Cretaceous rocks, leading to the discovery of Angolatitan. The discovery was made by Octávio Mateus on May the 25 near Iembe in the province of Bengo, and excavations were conducted during May and August 2006.^[1]

Angolatitan was described by Octávio Mateus and colleagues in 2011. The generic name means "Angolan giant". The specific name is derived from Adamastor, a mythological sea monster that represented the dangers Portuguese sailors faced in the southern Atlantic.^[1] Until 1975, Angola was a Portuguese colony.

Description

The only specimen is a partial right forelimb, including shoulder blade, upper arm bone, the two bones of the lower arm (ulna and radius), and three metacarpals. These fossils (Field number MGUAN-PA-003) are stored in the Museu de Geologia of the Universidade Agostinho Neto in Luanda.^[1]

The upper arm bone measures 110 centimetres (43 in), the ulna 69 centimetres (27 in) in length. In general, the forelimb was less robust than in most of the more derived titanosaurs. The metacarpals were slender and equal in length; those of titanosaurs were more robust with varying lengths. Unlike titanosaurs, the olecranon was absent, and the first metacarpal was not bowed.^[1]

Classification

Angolatitan was a basal titanosauriform, more derived than Brachiosaurus but less derived than Euhelopus and Titanosauria, which is notable given its relatively late appearance in the sauropod fossil record.

Recent phylogenetic tests run by Gorsack and Connor (2017) recover Angolatitan as a non-titanosaurian titanosauriform.^[2]

Palaeoecology

The specimen was found in a 50 m thick subsection of the Itombe Formation called the Tadi Beds. The Itombe Formation was considered Turonian in age, but new data suggests that it dates to the Coniacian.^[3] These rocks were deposited under marginal marine conditions; fossils include ammonites, echinoderms, and fishes (including sharks). Tetrapods include the turtle Angolachelys mbaxi, the mosasaurs Angolasaurus bocagei and Tylosaurus iembeensis, and several plesiosaur fossils.^[1]

The ecosystem inhabited by Angolatitan would have been desert-like. Presumably, this sauropod would have been well adapted to very dry conditions, similar to extant desert elephants.^[1]

References

1. Mateus, O.; Jacobs, L.L.; Schulp, A.S.; Polcyn, M.J.; Tavares, T.S.; Neto, A.B.; Morais, M.L.; Antunes, M.T. (2011). "Angolatitan adamastor, a new sauropod dinosaur and the first record from Angola" (PDF). Anais da Academia Brasileira de Ciências. 83 (1): 221–233. doi:10.1590/S0001-37652011000100012. ISSN 0001-3765. PMID 21437383.
2. Gorscak, E.; O'Connor, P. M.; Roberts, E. M.; Stevens, N. J. (2017). "The second titanosaurian (Dinosauria: Sauropoda) from the middle Cretaceous Galula Formation, southwestern Tanzania, with remarks on African titanosaurian diversity". Journal of Vertebrate Paleontology. 361 (4): 35–55. doi:10.1080/02724634.2017.1343250. S2CID 90885040.
3. Mateus, Octávio; Callapez, Pedro M.; Polcyn, Michael J.; Schulp, Anne S.; Gonçalves, António Olímpio; Jacobs, Louis L. (2019). "The Fossil Record of Biodiversity in Angola Through Time: A Paleontological Perspective". Biodiversity of Angola. Springer International Publishing. pp. 53–76. doi:10.1007/978-3-030-03083-4_4. ISBN 978-3-030-03082-7. S2CID 133717540.