Describer

Mateus, 1998

Time

Jurassic Late

Classification

Saurischia Theropoda Tetanurae Carnosauria Allosauridae

Diet

Carnivore

Fossilsite

Lourinha, Portugal

Info

Genus - Typespecies

Mateus, O. (1998) Lourinhanosaurus antunesi, a new Upper Jurassic Allosauroid (Dinosauria: Theropoda) from Lourinha (Portugal). Memorias da Academia de Ciencias de Lisboa. 37: 111-124

Abstract

A new Allosauroid dinosaur (Saurischia: Theropoda) was found at Peralta near Lourinhã, Portugal (Upper Jurassic, upper Kimmeridgian/Lower Tithonian). It is described under the name Lourinhanosaurus antunesi n. gen., n. sp. The corresponding diagnosis is as follows: all vertebrae are longer than tall; the neural spines of the anterior caudal vertebrae present a well-developed spike-like anterior process; the pubic blade is perforated by a large vertical ellipsoidal foramen; and the lesser trochanter is well separate from the shaft of the femur in lateral view. Thirty two gastroliths have been found in the rib cage. This is the first non-avian theropod found in association with gastroliths.

Introduction

Mesozoic reptile remnants have been reported from Portugal since long ago (Sauvage, 1897-98; Zbyszewski, 1946; Lapparent and Zbyszewski, 1957; Antunes, 1976; and Galton, 1980, 1991; among others). Recently a theropod nest with about 100 eggs was found at Paimogo, Lourinhã (Mateus et al., 1997) about 7 km from the site where the specimen described here was found.

In the Lourinhã area (mainly Upper Kimmeridgian and Lower Tithonian levels) were discovered several dinosaur remains ascribed to Brachiosaurus atalaiensis (Sauropoda), Dacentrurus armatus (Stegosauria), Dracopelta zbyszewskii (Ankylosauria), Hypsilophodon sp. (Ornithopoda), Megalosaurus insignis and Megalosaurus pombali (Theropoda regarded as nomina dubia by Molnar, 1990) as well as to an unidentified Ceratosauria. Other remains were ascribed to unidentified sauropods and an unidentified Ornithopod (Galton, 1980; 1991; Helmdach, 1973-74; Lapparent & Zbyszewski , 1957; and unpublished data)

In 1982 a farmer (Mr. Luis Mateus) discovered an incomplete dinosaur skeleton with bones from one individual still in anatomical connection that he removed and offered to the GEAL- Museum of Lourinhã, where they are kept. Parts of the bones were already without the hard sediment cover. Unfortunately the bone-containing block was broken in order to make the transportation easier.

Systematic palaentology

inosauria Owen, 1842

Saurischia Seeley, 1888

Theropoda Marsh, 1881

Avetheropoda Paul, 1988

Allosauroidea Currie & Zhao, 199

Lourinhanosaurus gen. nov.

Lourinhanosaurus antunesi nov. sp.

Abbreviations

GEAL- Grupo de Etnologia e Arqueologia da Lourinhã; ML Museum of Lourinhã.

Etymology- Derivatio nominis Lourinhanosaurus refers the area (Lourinhã, Portugal) where the specimen was found; antunesi after Professor Miguel Telles Antunes, Portuguese palaeontologist.

Holotype

ML370. Remnants from a single individual: axial skeleton (six cervical vertebrae with 6 ribs, five dorsal vertebrae with ribs, 5 sacral vertebrae, 14 caudal vertebrae with 8 chevrons). Appendicular skeleton: femora (left femur without tibial and fibular condyles; in right femur lacks the proximal end); 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 (?). Associated material: 32 gastroliths

Generic diagnosis

As shown below, the Peralta (Lourinhã) dinosaur can be assigned to the Allosauridae. This specimen differs from all the others in the group because all vertebrae are longer than tall; by the neural spines of the anterior caudal vertebrae with a well-developed spike-like anterior process; by the pubic blade perforated by a large vertical ellipsoidal foramen; and by the lesser trochanter well separated from the main body axis of the femur in lateral view. These characters point out to a new genus to which the name Lourinhanosaurus is given.

Type species

Lourinhanosaurus antunesi sp. nov.

Species diagnosis

As for the genus (see above).

Locality and age

The dinosaur was discovered at Peralta, about 75 Km NW of Lisbon (Portugal), near Lourinhã (UTM coordinates: MD707443) - Upper Jurassic (Upper Kimmeridgian/Tithonian, Sobral Unit) according to Manuppella (this volume). The remnants are preserved in a gray, micaceous, fine sandstone.

Description

The holotype of Lourinhanosaurus antunesi corresponds to a partial skeleton that was found lying on its right side. It comprises part of the axial skeleton, pelvis girdle and hindlimb in anatomical connection, and do not show any deformation.

Vertebrae

The neural arch is fused to the centra. All vertebrae are longer than high which is a diagnostic feature, not showed in any other similar theropod. All cervical vertebrae found were in articulation. The cervical centra present one pair of pleurocoels. The centra are strongly opisthocoelous. The ventral surface presents a median keel. In articulation the cervical series describe a curve concave in dorsal view. There are paired ribs. Diapophyses are reduced.

The eleventh to fourteenth dorsal vertebrae are present in Lourinhanosaurus considering that had 14 dorsal vertebrae, the same number as in Sinraptor (Currie & Zhao, 1993), Allosaurus (Madsen, 1976), and Acrocanthosaurus (Stovall & Langston, 1950). The centra of the posterior dorsal vertebrae are amphicoelous and relatively longer than in Allosaurus fragilis. The centra are not pleurocoelous. The dorsal vertebrae exhibit prominent neural spines and zygapophyses.

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

All the caudal vertebra centra are longer than high. The caudal centra are neither hollow nor cavernous. The anterior caudal vertebrae are moderately amphicoelous. There is a longitudinal groove at the ventral surface of the anterior caudal centra. A decreasing, transverse process is present, at least, to the fifteenth caudal vertebra. Neural spines decrease in size caudalwards. The transverse processes are long and placed near the middle of the centrum.

The neural spines of the anterior caudals are thin and blade-like with a spike-like anterior process. The anterior processes of the caudal neural spines are more or less developed amongst allosauroids but not so much as in Lourinhanosaurus. The neural spines are present in the caudal vertebrae until, at least, the fifteenth caudal vertebrae. Except for the first caudal vertebrae the centra have an anterior and posterior chevron facet and the corresponding chevron. The chevrons are deeper than long and not distally expanded. The chevron shafts are slightly curve posteriorly. The chevron bases have paired anterior and posterior processes. The haemal canal is close to the proximal end.

Pelvic Girdle

The three pelvic elements are not fused.

In lateral view the posterodorsal margin of the ilia is somewhat curve ventrally (in lateral view). The posterior end of ilium is pointed, and less truncated than in Allosaurus. Almost whole of the blade border bears some roughness corresponding to pelvic muscle\\\'s insertions. The preacetabular portion is expanded dorsoventrally; the postacetabular portion is significantly longer than the preacetabular one. Pubic peduncle forms an angle of nearly 45º with the main axis.

The anterior end is expanded and projects slightly beyond the pubic peduncle. The posterior end is much more expanded beyond the ischial peduncle. The medial blade is fused to the fifth sacral vertebra. The pubis peduncle is longer than the ischial peduncle but both are at the same level. The pubic peduncle is twice as long anteroposteriorly as broad transversely.

The two pubes are in articulation. The pubis is strong and straight, with postero-proximal expanded ischiac articulation. The pubic plate presents a large, vertical ellipsoid pubic foramen or fenestra. The border of the acetabulum is longer than in Allosaurus fragilis. Unfortunately the distal ends of both pubes are not complete and the presence of the pubic boot, which is very diagnostic of the Allosauridae (Holtz, 1994), cannot be ascertained.

The ischium projects caudoventrally. The shaft is straight with a minimum diameter of 2.2 centimetres. There is a slender \\\"neck\\\" at the pubic peduncle. The obturator process is placed proximally. Its shape is trapezoidal (it is narrower near the ischial shaft than at the anterior edge). There is a notch between the pubic and obturator processes.

Hindlimb

The femoral head is medially directed. The fourth trochanter is long and it is situated on the posterior surface of the femoral shaft where there is an obvious muscle scar. The length of the fourth trochanter is at least twice the femur shaft diameter just below. The greater trochanter does not bear a cleft. It presents an aliform lesser (or anterior) trochanter extended by a distally placed lamella of bone, well separated from the main body of the femur in lateral view.

The distal condyles are separated by a deep intercondylar groove. This groove is more developed posteriorly than anteriorly. There is no crista tibiofibularis (which is characteristic of Ceratosauria).

The shaft of the fibula is slender and straight. It expands proximally, being convex in lateral view and concave in medial view. The distal end is lacking.

Table 2 Measurements of ML370 Lourinhanosaurus antunesi

Greatest length of Ilia* 46.0

Diameter of femoral midshaft 5.2

Length of femur * 54.0

Width of proximal end of fibula 7.9

Width of proximal end of tibia 12.7

Measurements in centimetres.

*- Estimated measurement.

Associated material

Gastroliths

Gastroliths have been described in Ornithopoda, Ceratopsia, Prosauropoda, Sauropoda, Lacertilia, Crocodylia, extant birds and seals (Stokes, 1987; Christiansen, 1996) but not in non-avian theropods until now. The specimen had 32 gastroliths and the enveloping sediment preserved the negative imprint of 3 additional gastroliths. The maximum observed gastrolith length is 22 millimetres. Near the pebbles were three small bone fragments that seemed to be food remains. The gastroliths have been found in the rib cage below the eleventh dorsal vertebra. The high number, concentration and relative size of the gastroliths suggest that they belong to this specimen, and that they had not been swallowed when eating other dinosaur\\\'s stomach.

Discussion

This specimen shares the following theropod synapomorphies: presacral vertebrae with pleurocoels; five sacral vertebrae; long preacetabular process on the ilium; pronounced brevis fossa on the caudal part of the ilium; femur cranially convex; fibula closely appressed to the tibia and attached to a tibial crest; and thin-walled, hollow, long bones (see Gauthier, 1986). The species is clearly a tetanuran and avetheropod (neotetanuran sensu Sereno et al. 1994, Allosauridae + Coelurosauria) because the chevron bases have paired anterior and posterior processes, the iliac-ischial articulation is smaller than the iliac-pubic articulation, the ischial obturator notch is present, the femoral anterior trochanter is blade-shaped, there is an iliac preacetabular fossa, and the iliac pubic peduncle is twice as long anteroposteriorly as broad transversely (Sereno et al, 1996).

No features referred by Sereno et al (1994; 1996) are available to ascribe Lourinhanosaurus to the Allosauroidea because only cranial characters were used. However because of the least than 20% broader than tall mid cervical centra, the elevation of the anterior face present in mid cervical centra, the developed lesser trochanter, the presence of more than 15 caudal vertebrae with transverse processes, the trapezoidal ischial obturator flange and the reduced fibular fossa it is possible to classify this specimen as a non Carcharodontosaurid nor Coelurosaurian [ Avetheropoda].

Holtz (1994) produced a single, most parsimonious cladogram of the Theropoda. The data-matrix was criticised by Clark et al. (1994) and Charig & Milner (1997). Holtz (1995, 1996) and Sereno et al (1996) published new theropod relationship data. Using the data-matrix of Holtz (1994) with the changes introduced by Charig & Milner (1997) the specimen from Lourinhã may be placed as a basal [Avetheropoda] Paul, 1988. For this study the Hennig86 programme was run. The cladogram has a consistency index (C.I.) of 49%, a retention index (R.I.) of 70% and 236 steps length.

The data-matrix of Sereno et al. (1996) was also run in Hennig86 with Lourinhanosaurus characters showing a C.I. of 81%, R.I. of 84% and 80 steps length. Lourinhanosaurus was placed within the Neotetanurae in a polytomy among Sinraptoridae , Crylophosaurus, Monolophosaurus, Allosaurus and Carcharodontosauridae .

The following features justify including Lourinhanosaurus in the Allosauroidea: transverse processes of middle caudal series placed near the middle of the centrum rather than posteriorly on the centrum; slender \\\"neck\\\" at the pubic peduncle of the ischium; ischium with trapezoidal (in lateral view) obturator process; small notch at the distal end of the ischial obturator process; and aliform lesser trochanter. This specimen differs from all other allosauroids because all vertebrae are longer than tall, the neural spines of the anterior caudals vertebrae possess a well-developed spike-like anterior process; the posterior end of ilium is pointed, not truncated; and the pubic blade is perforated by a large vertical ellipsoid fenestra.

Three genera have been reported to the Allosauridae: Allosaurus , Neovenator and Saurophaganax (Chure, 1995; Hutt et al., 1996). Smith (1998) reclassified Saurophaganax maximus into the genus Allosaurus as [Allosaurus maximus]. Acrocanthosaurus was ascribed to Allosauridae (Holtz, 1994) and to the Carcharodontosauridae (Sereno, 1996). The Sinraptoridae (comprising the genera Sinraptor, Szechuanosaurus, and Yangchuanosaurus) and Carcharodontosauridae (with the genera Carcharodontosaurus, Bahariasaurus and Giganotosaurus) are related to the Allosauridae (Currie & Zhao, 1993; Holtz, 1996; Sereno et al., 1996). The taxonomic position of Chilantaisaurus, Crylophosaurus and Monolophosaurus remains uncertain.

Neovenator salerii is the only Allosaurid known in Europe so far (Hutt et al., 1996). However Lourinhanosaurus is distinct from Neovenator by the not pleurocoelous last dorsal vertebrae, and by the position of the fourth trochanter on the posterior surface of the femoral shaft in Lourinhanosaurus antunesi. Several features are similar to those found in Allosaurus, trapezoidal ischial obturator process and aliform lesser trochanter (Madsen, 1976). However it differs from Allosaurus by the proportionally longer vertebrae, the less developed cnemial crest of the tibia and by the other diagnostic characters referred to above. The chevron of Saurophaganax differs from those in Lourinhanosaurus by its distal expansion. In Saurophaganax the shape of the ischial and pubic obturator processes are different from those of the Portuguese dinosaur.

The reduced cervical diapophyses are more similar to Sinraptor than to Allosaurus fragilis. The neural spine is much less developed than in Acrocanthosaurus atokensis. The trapezoidal obturator process is placed proximally as in Allosaurus fragilis (Madsen, 1976), or in Acrocanthosaurus atokensis (Stovall & Langston , 1950).

The pubic blade gap in Lourinhanosaurus could result from the fusion of the pubic fenestra with the pubic obturator foramen (the two gaps, pubic fenestra and obturator foramen, are present in Coelophysis (Colbert, 1989) and Syntarsus (Raath, 1980)), or an enlargement of the obturator foramen present in non avetheropoda as Piatnitzkysaurus, Torvosaurus and Carnotaurus as well in Monolophosaurus (Zhao & Currie , 1993), and in the sinraptorid Yangchuanosaurus shangyouensis (Dong et al. , 1983). Taking into account that the latter two species belong to the allosaurids (see Holtz, 1996), the enlargement of the obturator foramen is the more probable hypothesis. Sinraptor has a quite similar, smaller opening which forms an obturator notch. This similarity suggests that Lourinhanosaurus is more primitive than the allosaurids. It therefore may probably be a sinraptorid. Accordingly that the Lourinhanosaurus could be the only sinraptorid known in Europe so far.

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