The yellowish sandstone of the
Lossiemouth Sandstone Formation can be found on the coast near Elgin, in the
Moray council area, north east of Scotland (Fig 1). Fossils were collected
there in different quarries, around the town of Lossiemouth, at the end of the
19th and beginning of the 20th century, notably by the ardent collector William
Taylor of Lhanbryde (1849-1921). The sand from the sandstone was probably
carried by wind and deposited over a fluvial area, indicating that the location
during the Late Triassic was a sand dune desert with narrow strips of lowland
vegetation around rivers. The sandstone did not preserve any index fossil such
as pollens, plants or invertebrates, and no radiometric dating could be
performed, leading to some uncertainties on the exact age of the rocks.
However, based on the correlation of the Lossiemouth vertebrate fauna with
those of the Maleri Formation of India, the Santa Maria Formation of Brazil,
the Ischigualasto Formation of Argentina, a Late Carnian age is generally
attributed to the sandstone. The fauna is represented by eight taxa of
reptiles, including six archosaurs.
Fig. 1.- Location of the
Lossiemouth Sandstone Formation today (left) and during the Late Triassic
(right).
Saltopus elginensis Huene, 1910 ("Elgin's hopping foot"), is
known from a single badly preserved skeleton. The exact affinity of this small
(60 cm long) bipedal predator has been debated for decades. It was at some
point classified as an early theropod dinosaur but more recent analysis put it
within the dinosauriformes but outside the Dinosauria clade as a sister taxon
to them (It means Saltopus is not a dinosaur but one of its closest
relatives). Since the skull in the fossil is missing, the diet of this animal
is unknown.
Another interesting animal from the
Carnian of Scotland is Scleromochlus taylori Woodward, 1907
("Taylor's hard fulcrum") (Fig 2). This rather strange 1.8 m long
creature looks a bit like a lizard on long slender legs. It was related or even
has been considered ancestral to the pterosaurs, a group of archosaurs that
will eventually conquer the air.
Several skeletons of this animal are known.
Fig 2.- Reconstruction of Scleromochlus
taylori.
The 4 meter long and probable top
predator of its time, Ornithosuchus longidens ("long-toothed bird
crocodile") (Huxley, 1877) (Fig. 3) belongs to another group of
facultative bipedal carnivorous reptiles distantly related to crocodiles, the
Ornithosuchians. They were equipped with sharp teeth and a row of bony scales
(osteoderms) along their back and tail. Ornithosuchus was once thought
to be ancestral to the theropod dinosaurs, but details of its skeletal anatomy
such as the braincase and the configuration of the ankle show that it was a
Crurotarsi like the Rauisuchians, the Aetosaurs, crocodiles and phytosaurs and
not an Avemetatarsalia (Dinosaurs and Pterosaurs).
Fig. 3- Reconstruction of Ornithosuchus
longidens.
Erpetosuchus granti Newton,
1894 ("Grant's Snake Crocodile") was a small (60 cm long) agile
quadrupedal predator that might have hunted small lizards and amphibians (Fig 4). Erpetosuchus was the Lossiemouth fossil the most closely related
to modern crocodiles and is known from at least four specimens. Considering the
location of Scotland at that time (Fig 1), it is no surprise that an
additional fossil referable to the same animal was discovered in the New Haven
Formation of Connecticut, United States.
Fig. 4.- Reconstruction of Erpetosuchus
granti.
Herbivores are represented by
several groups of reptiles. The rhynchosaurs had stocky bodies with a broad
skull and a powerful beak. They may have fed on tough vegetation, such as the
seed ferns which were abundant at that time. In Europe, Rhynchosaurs were
represented by the 1.3 meter long Hyperodapedon
gordoni Huxley, 1859 ("Gordon's best pestle tooth") from Scotland
(Fig. 5). It is known from at least 35 individuals, making it the most
abundant vertebrate fossils of the formation. The fossils came into various
sizes, reflecting ages, that can be grouped into two general types
(morphotypes) possibly indicating sexual dimorphism. The genus Hyperodapedon
had a worldwide distribution, with several species described from India,
Brazil, Argentina. Zimbabwe, Madagascar, Tanzania and the United states. They
had therefore been used to correlate different formations across the globe,
serving as an "index" fossil.
Fig. -5. - A pair of Hyperodapedon
gordoni.
Aetosaurs were heavily armored archosaurs, with a body covered with
plate-like scutes (osteoderms) and spikes. These vegetarian animals were also
distantly related to crocodiles and are now thought to have been fully terrestrial
animals. The carnian representives in Europe include the genera Stagonolepis
and Paratypothorax, with Stagonolepis robertsoni Agassiz, 1884
("Robertson's pitted scale") being the Lossiemouth species (Fig. 6). It measured about 3 meters in length. The remains of Stagonolepis
were originally mistaken for fish scales, thus the generic name.
Fig. 6.- Stagonolepis
robertsoni.
Procolophonids were small lizard
like creatures belonging to the ancient lineage of reptiles called
Parareptilia. By the end of the Triassic they have adopted a vegetarian diet
before being wiped out by extinction at the end of the period. Leptopleuron
lacertinum Owen, 1851 ("Lizard slender ribs") is a typical
procolophonid that measured about 30 cm in length (Fig 7). It might have
lived in burrows. This little critter was the subject of a bitter
rivalry between famed paleontologists Richard Owen and Gideon Mantell at the
end of the 19th century, both wanting to be first to describe the animal.
Mantell christened the fossil Telerpeton elginense but Owen was quicker
to publish so the name he gave has priority according to the international
rules of nomenclature.
Fig. 7.- Reconstruction of Leptopleuron
lacertinum.
The rhynchocephalians (and more
restrictively, the sphenodontians) were once a successful and diverse group
of lizard-like mesozoic reptiles with both aquatic and terrestrial forms. The
only modern surviving member of the rhynchocephalians is the tuatara (Sphenodon)
from New Zealand, generally presented as a true "living fossil". The
Lossiemouth sandstone has yielded the species Brachyrhinodon taylori
Huene, 1910 ("Taylor's short nose teeth") (Fig. 8) which was very
similar to the tuatara in shape, but smaller, measuring some 25 cm in length,
and with probably a similar lifestyle. Both Leptopleuron and Brachyrhinodon
are known from numerous specimens.
Fig -8.- Reconstruction of
Brachyrhinodon taylori.
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