Go to: Excavations Vertebrate
Remains
This article has largely been derived from my reading of:
The pioneer of the Jurassic Guimarota locality was Professor Walter Kühne. This German
paleontologist had emigrated to Britain in the late 1930s, before returning in 1952.
Unusually for the time, he had a particular interest in Mesozoic mammals. As not many sites
were then known in Europe, he set about finding some more. The best method of locating the
previously undiscovered lies in looking in the right places. Geological maps provide
information about the age and details of rock formations. After identifying possible
locations, Kühne took to the road to look at the rocks. His first forays into Iberia in the
early 1950s centred on the southern Pyrenees. His attention was attracted to Portugal by a
paper published on dinosaurs. In September 1959, Kühne and Frey, a student, went to
prospect the localities concerned. That's when they heard about the last working coalmine
in the Lusitanian Basin; Guimarota on the outskirts of Leiria.
The newly-mined coal contained small shells which suggested it had been laid down in
lime-rich water. Such conditions are favourable for the preservation of vertebrate fossils.
Closer inspection revealed fragments of turtle shell, crocodile armour and fishscales. Frey
found something else in one lump. It was part of the skull of a multituberculate mammal.
Whilst that might be termed a stroke of luck, there had been years of method involved in
this madness. The following year, (1960), Professor and Frau Kühne returned with two
students from Berlin. Further mammal fossils came to light. The work was aided by the mine
foreman, who initially sorted the material according to size. Three local women became
involved in processing. The number of specimens grew. Expeditions continued, personnel
increased for a couple of years, methods improved, and so did the variety of fossils. Other
sites in Iberia were also identified. As these came under closer examination, work at
Guimarota slowed, (1963), and eventually ended, (1968).
In part, this was because the mining company had gone bankrupt, but it also seemed probable
that the coal had been thoroughly sampled. Furthermore, Kühne privately stated that an
aversion to routine was significant. Those new sites and new possibilities were more
attractive.
Given the rarity of Mesozoic mammal remains, the work at Guimarota had been a resounding
success. Over 70 jaws, fragments and near complete skulls and well over a thousand isolated
teeth represented a relatively enormous harvest. This mine was the richest site for
Jurassic mammals then known.
Kühne was a senior Professor at the Freie Universität in Berlin. With the variety of remains
from Guimarota, some of his colleagues thought further fieldwork there worthwhile. Not
unreasonably, Kühne felt other locations offered more promise. They did produce results,
(eg. Port Pinheiro), but nothing like the success of Guimarota. Prospecting further afield
in Morocco and Iran proved even less successful.
Back in Berlin, pressure was building for a return to Guimarota, but Kühne wasn't in favour.
Due to the structure of universities at the time, the opinion of this senior academic
carried great weight. However, against a background of widespread unrest and activism,
liberalising reforms in 1968 meant that fieldwork could resume with or without his
blessing.
The mine was visited in 1971. Other than for part of the entrance hall, most the former
buildings had been demolished and an orchard of peach trees planted. The land now belonged
to a man newly arrived from Angola, (then a Portuguese colony). He wasn't inclined to allow
any work to begin, but he was keen to find a supply of water for his own needs. The
probability that the redundant coalmine had been flooded awakened his interest. The
entrance was reopened. Despite being submerged, at least the brick supported entrances to
the shafts were intact.
The water, plus the promise of a high rent for a derelict, partial entrance hall, reduced
the landowner's reluctance. However, he refused to allow any coal to be left on his land,
so it had to be returned to the mine after processing. (At the height of subsequent
operations, this involved a metric ton of coal a day.) Whilst all this was technically
possible, it would clearly also be extremely labour and money intensive. That Kühne found
the idea crazy is not so surprising, especially as no other institutions could be persuaded
to join the project. With the benefit of foresight, pumping so much effort into pumping out
an already extensively sampled coal seam, would probably mean effort down the drain.
In 1972, a grant application for a project called 'Mammals in the Mesozoic' was accepted by
the Deutsche Forschungsgemeinschaft. The award was extended four more times on a yearly
basis. Due to regulations, further support from that source wasn't available. By widening
the scope of study to other vertebrates and the paleo-environment, the Freie Universität
itself provided a special research grant to cover costs for five more years. The total bill
for the decade worked out at over DM800,000. In European paleo-funding times, that was
massive. Eventually, the money was running out, the structure of the mine was deteriorating,
and the equipment was growing ever less co-operative with age. Excavations ceased in 1982
and the site was left to reflood. New taxa weren't identified during the final years.
The effort was more than handsomely rewarded. The number of mammalian teeth recovered is
about ten thousand. There are well over a thousand jaws, twenty skulls and two near
complete skeletons. The numbers or cartilaginous and bony fish, amphibian, turtle, lizard,
crocodile, pterosaur and dinosaur specimens aren't yet clear. Although it's now over twenty
years later, only the mammal remains have been fully prepared, at least as things were
identified during fieldwork. There's plenty more work to be done.
Go to: Excavations Vertebrate
Remains
This article has largely been derived from my reading of:
The fossils of Guimarota come from a coalmine, but the preservation conditions for vertebrates
in coal are usually poor. Decaying plants, (the basis of coal), produce corosive acids
which tend to destroy the remains. But, if the effects are neutralized by lime, the
possibility equations change radically. Such coal seams can be treasure houses; eg.
Guimarota. To suggest a further example, why not go fossiling in the Everglades of Florida
in fifty or a hundred-and-fifty million years time? They're also on top of limestone
deposits. Although the plants and animals are very different, it's not a bad analogue for
conditions at Guimarota during the Upper Jurassic.
"Most vertebrate remains are not preserved in articulation and they are often
fragmentary; articulated remains are extremely rare", (p.133). The possibilities of
articulated remains being preserved were also subject to biases of skeletal construction
and lifestyle. Compared to aquatic vertebrates, the remains of terrestrial ones had to be
transported over longer distances before deposition. The mammals didn't generally jump
into the swamp in order to die. The already deceased animals had to be carried by some means
or other; river action is a likely mechanism. Coupled with the relative fragility of small
skeletons, the rareness of articulated specimens, (let alone near complete ones), is easy
to understand.
Plants
Shelled creatures
Fish
Amphibians
Reptiles
Also present are crocodiles. In this case, some articulated finds have been made. This
indicates that the individuals were burried shortly after death. These remains also show
few signs of abrasion. Along with the presence of tens of thousands of teeth, these are
indications that some crocs were generally resident in the area of deposition. The most
frequently found and best represented genus is Goniopholis. Most other genera
probably lived further inland; eg the small and entirely terrestrial Lisboasaurus.
Turtles are common. However, despite the protection afforded by a shell, virtually only
isolated fossils have been recovered. One suggested explanation is that most remains may
be from less robust juveniles. Abrasion damage is insignificant.
Pterosaurs had bones adapted for lightness. Whilst good for flight, that's bad in terms of
preservation prospects. However, if they'd been aware of this deficiency, I doubt the
pterosuaus would've minded. Postcranial remains are represented by rare, and badly preserved
bits of leg and hips. Several hundred teeth have been recovered. Also known are a few teeth
referrable to Archaeopteryx. Though far less spectacular than the gobsmacking fossils
of Solnhofen, Bavaria,
these Portugese specimens are presently the oldest generally accepted bird remains in the
world. Also present in the fauna are both dromaeosaurid and troodontid dinosaurs. Both
families are thought to be close relatives of birds, and are best known from the
Cretaceous.
Mammals
The following genera have been described:
Multituberculata:
Dryolestida:
Stem-Zatheria:
Disarticulation
Portugal in the Mesozoic
Lusodinos
Mesozoic Eucynodonts, Location Summaries
Information on the Book, Guimarota - A Jurassic Ecosystem can be found at.
Trevor Dykes (not a paleontologist) 22.1.2004 Latest update: 27.1.2004
The Excavations of Guimarota, Upper
Jurassic of Portugal
Krebs B (2000), The excavations in the Guimarota mine, p.9-20, in Martin T &
Krebs B (eds), Guimarota - A Jurassic Ecosystem, Verlag Dr Friedrich Pfeil, München.
The Vertebrate Remains and Paleoecology
of Guimarota, Upper Jurassic of Portugal
Gloy U (2000), Taphonomy of the fossil lagerstatte Guimarota, p.129-136, and
Martin T (2000), Overview over the Guimarota ecosystem, p.143-146. Both articles are
in Martin T & Krebs B (eds), Guimarota - A Jurassic Ecosystem, Verlag Dr Friedrich
Pfeil, München.
Most plant remains are small and suggestive of a subtropical climate. Bodies of water seem
to have been lined with horsetails, (Equisetites), a plant group which used to be far more
diverse than the remnant populations alive today. The forest was dominated by conifer trees,
whilst tall ferns and ginkgo trees were also present. The undergrowth was characterized by
various ferns.
Mollusks are common but not diverse. Most specimens so far have been referrable to a couple
of genera; Isognomon probably favoured brackish habitats, whilst "Unio"
was possibly a true freshwater clam. Occasional snails suggest a near-coastal lifestyle,
although one genus, Melampoides probably lived mostly on the land. Tiny shelled
animals called ostracodes frequently provide helpful information for paleontologists and
geologists. The fossilized ones of Guimarota provide further support for the presence of
brackish conditions. Furthermore, as with the mammals and dinosaurs, they show taxonomic
affinities with their counterparts from the Upper Jurassic Mid West of North America.
Sharks and relatives have skeletons made from cartilage rather than bone. The chances of
preservation are poor. Finds are generally restricted to isolated teeth, scales and
occasional spines from heads and fins. As some types have many teeth, (subject to ongoing
replacement), and teeth are hard, these are far and away the commonest elements at
Guimarota. The most commonly represented group are hybodont sharks, which were adaptable
in terms of tolerance to differing concentrations of salt.
Several groups of bony fish are represented, and there are a few isolated bits of skeleton.
Only one partial skull has been identified. As such specimens were carefully looked out for
when the coal was being split, their general absence suggests the skeletons were
disarticulated before deposition.
Most common are thousands of fragments of a family called Albanerpetontidae. These isolated
bones often show breaks, but not abrasion. This suggests they weren't transported to the
site by rivers. These small animals probably lived in the general area, which would also
help account for their relative abundance. They may well have been borrowers, and would
have been well-suited to conditions provided by thick vegetation and soft ground. As yet,
studies of the amphibians are still at a relatively early stage.
Biases of size and lifestyle also influenced the fossilization prospects for these
creatures. Aquatic and semi-aquatic forms were favoured; turtles and crocodiles. Landlubbers,
(lizards and dinosaurs), had to be transported. If, as seems probable, this was a swamp,
there would also have been a possible bias against the presence of larger representatives.
A five ton carnivore isn't likely to go walking on boggy ground. It'd sink. Remains of
large dinosaurs are extremely rare here.
The lizards are diverse. There are three genera of skink and two representatives of
Anguimorpha. One of the skinks is small and worm-like in shape, which may indicate a
further burrower. A larger taxon is a long-snouted, proto monitor lizard.
With few exceptions, the dinosaurs represented were less than two metres long, and
frequently less than one metre. Whether these were juveniles or small taxa is not clear
due to the state of preservation. 90% of the teeth are from meat-eating theropods.
Two large fragments of snout and some other bits and pieces represent Machimosaurus,
which was a fully marine crocodile. The individual must've been about nine metres long. It
was presumably a chance visitor, whose stay outlasted its expectations.
The wealth of material outlined above is mainly composed of isolated finds. Robust body
parts, such as a few limb bones and many jaws, are generally well preserved. The two
articulated skeletons are exceptions. They must have been entombed rapidly by sediment.
Docodonta:
Haldanodon.
Docodonts are the most basal group of mammals present. The lower jaws contained a couple
of postdentary bone which, in more derived mammals, can be found inside the inner ear,
(malleus and incus).
Bathmochoffatia;
Guimarotodon;
Henkelodon;
Kielanodon;
Kuehneodon;
Meketibolodon;
Meketichoffatia;
Paulchoffatia;
Plesiochaffatia;
Proalbionbaatar;
Pseudobolodon;
Xenachoffatia.
Multis seem to have been the equivalent of rodents in the northern hemisphere of the
Mesozoic. They're not related to any existing mammals, and the line went extinct thirty to
forty million years ago.
Drescheratherium;
Dryolestes;
Guimarotodus;
Henkelotherium;
Krebsotherium.
Dryolestidans, (and especially dryolestids), are the most common mammal fossils in the
fauna. This order was a fairly early radiation of crown-group mammals. As well as the
family Dryolestidae, it also includes paurodontids such as Henkelotherium.
Nanolestes.
This genus is the most derived mammal in the fauna, and is more closely related with
modern mammals.
Various factors can be cited to account for the generally disarticulated state of the remains,
and the contribution of transportation has already been mentioned. The presence of fish and
shark teeth indicates the availability of hungry mouths. Given its inability for either
fight or flight, dead meat is popular amongst many predators. Also active would have been
the normal processes of disintegration upon floating corpses, and the currents pushing
material around before burial.
Pedro Andrade has a homepage focussing on the dinosaurs of Portugal (and elsewhere).
This includes articles on paleo-themes and classification, a gallery of his artwork,
information on fossil localities and more besides.
Dinosauria.Pt
http://www.oocities.org/lourinhanosaurus/
The distant past of Portugal. This is part of a wider project on dinosaurs in general:
(http://www.oocities.org/dinosauria_pt).
http://www.dinodata.net/lusodinos/
Octávio Mateus' website: "This is a page on Dinosaurs in general and Portuguese
dinosaurs in particular. It was thought to please professional and amateur palaeontologists
interested in Portuguese dinosaurs!"
It also features accessible scientific papers.
http:home.arcor.de/ktdykes/localities.htm
Reports on a variety of localities by Self MY.
http://www.pfeil-verlag.de/07pala/e2_80.html
A number of sample pages are included.
Mesozoic Mammals etc
http://home.arcor.de/ktdykes/meseucaz.htm