Lourinhanosaurus antunesi

 

A new allosauroid dinosaur (Saurischia: Theropoda) was found at Peralta, near Lourinhã, Portugal. It is described under the name Lourinhanosaurus antunesi n. gen., n. sp from the upper Jurassic.

This is the first theropod found in association with gastroliths.

Cladogramme of a Theropod, including the Lourinhanosaurus, based on Sereno et al. (1996). Octávio Mateus, (1998).

       Systematic:

                    Dinossauria Owen, 1842

                    Saurischia Seeley, 1888

                    Theropoda Marsh, 1881

                    Avetheropoda Paul, 1988

                    Allosauroidea Currie & Zhao, 1993

                    Lourinhanosaurus antunesi gen. et sp. nov.

32 gastroliths were found under the 11th dorsal vertebra. The widest one measures 22 mm. Among these stones there are bone fragments which can be presented as food remnants.

Gastroliths – stomach stones to help digestion.

The holotype presents the remnants of about 40% to 50% of the skeleton of a single individual, it shows part of the axial skeleton; the pelvic girdle and the front members in anatomical connection.

Lourinhanosaurus antunesi. Scale bar 0,5 m. Octávio Mateus, 1998 .

 

Axial skeleton: four complete cervical vertebrae; 1st, 11th, 12th, 13th and 14th dorsal vertebrae and five sacral vertebrae with the correspondent ribs.

Appendicular skeleton: femora (left femur without tibial and fibular condyles; the proximal end of the right femur is lacking), proximal part of the right tibia and fibula in anatomical connection; two ilia; proximal parts of both pubes and ischia and the proximal end of one metatarsus.

In every vertebrae the centra is longer than tall, this feature differs this specimen from all others in the allosauroidea group.

The neural arch is fused to the centra, so it’s possible to infer that the specimen is not a neonate nor a juvenile.

All cervical vertebrae were found in articulation.

The Lourinhanosaurus would have 14 dorsal vertebrae, this feature is common to the others Theropods to whom they are taxonomically close. The centra of the posterior dorsal vertebrae is amphicoelous but they are not pleurocoelous.

Five sacral vertebrae are present. Sacral centra are not pleurocoelous.

The caudal centra do not present any pleurocoelous and they are neither hollow nor cavernous. The neural spines of the anterior caudal are thin and blade-like with a spike-like anterior process.

Lourinhanosaurus antunesi gen. et sp. nov.
                            

A – Third caudal vertebra; B – Twelfth caudal vertebra.
Ap: anterior process of the neural spine; ns neural spine;
po: postzygapophyis; pr: prezygapophysis; tb: transverse process.
Scale bar 5 cm. Octávio Mateus, 1998.

    
    In what the pelvic girdle is concerned, the three pelvic elements (ilium, pubis and ischium) are not fused as they are in more primitive dinosaurs.     

Reconstitution of the pelvic girdle  of the Lourinhanosaurus antunesi gen. 
nov., sp. nov..Octávio Mateus, 1998

The femoral head is medially directed. The fourth trochanter is long and it situated on the posterior surface of the femoral shaft. The length of the fourth trochanter is at least twice the femur shaft diameter just below. It presents a lesser (or anterior) trochanter extended by a distally placed lamella of bone, well separated from the main body of the femur in lateral view.

Although uncompleted, the femur seems longer than the tibia.

 

Lourinhanosaurus antunesi gen. n., sp. n.
A - Left femur  in  lateral view;
B - Right femur in posterior view.
              h - femoral head; it - lesser or anterior trochanter;
                      tr4 - fourth trochanter. Scale bar 5 cm. Octávio Mateus, 1998

 

Lourinhanosaurus antunesi gen. n., sp. n.
Right tíbia and fibula  in lateral (A) and proximal (B) views.
cf - crista fibularis of tibia; cn - cnemial crest; fi - fibula
Scale bar 5 cm. Octávio Mateus, 1998

 

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