Sharks in Malta Part I - 'L-Ilsna ta' San Pawl'

The Sicilian Agostino Scilla was one of the first Europeans (together with Nicholas Steno in Denmark) to systematically study fossils and extract information about them empirically, as opposed to his contemporaries' tendency to attribute fossils to supernatural forces or a slew of mythical creatures.

Frontispiece of Agostino Scilla's 'La Vana Speculazione', 1670 - note the variety of fossils on the lower right

Both Scilla and Steno arrived to conclusions that were beginning to shape the science of geology as it is known today, in particular the then-controversial notion that fossils are derived from once-living organisms.

Interestingly, some of the fossils which both chose to illustrate in their works were obtained from Malta. These fossils are the famous glossopetrae (tongue stones), or, more accurately, fossil shark teeth, which during the Medieval, Renaissance and Baroque periods were considered to be a miraculous cure for a variety of ailments (Zammit Maempel, 1975; 1989). Malta was the centre of a lucrative business in these shark teeth and it is not hard to see how specimens could have come in Scilla and Steno's possession.

Carcharocles megalodon (Agassiz, 1843) teeth from the C2 Phosphorite Conglomerate, Malta

Most of these glossopetrae belong to the extinct Carcharocles megalodon (Agassiz, 1843), one of the largest fish ever to exist on Earth. An approximation of its size (in grey and red) compared to the modern (and morphologically similar) great white shark, Carcharodon carcharias (L., 1758) (in green) can be seen below.

The local name for these particular fossils is 'Ilsien San Pawl' (= St. Paul's Tongue) due to the belief that they formed inside the rocks while St. Paul was shipwrecked on Malta in the year 60 A. D. (Acts of the Apostles, 28: 2-7). During this episode, St. Paul shrugged off a snake which attacked him and threw it into an open fire, symbolically ridding the islands of poisonous 'vermin'.

'St. Paul's Shipwreck', by Stefano Erardi, 1683 - note the snake falling out of the main figure's hands into the fire

Carcharocles teeth from the collection of Sir Hans Sloane are also the oldest Maltese fossils in the British Museum (cf. Galea Bonavia, 2003).

References:

Galea Bonavia, C., 2003. Carcharocles megalodon (Agassiz) (Lamnidae: Neoselachae): A historical note. The Central Mediterranean Naturalist, 4 (1): 105.

Scilla, A., 1670. La vana speculazione disingannata dal senso: lettera responsiva circa i corpi marini, che petrificati si trovano in varii luoghi terrestri. Napoli: Colicchia.

Sloane, H., undated. Se la Virtu’ alessifarmaca della Terra, Glossopetre conchiti, Achini ed altre pietre figurate che si cavano dalle Rocche di Malta, sia innata o Miraculosa. Unpublished manuscript, Sloane Collection – British Library MS no. 763.

Zammit Maempel, G., 1975. Fossil sharks' teeth: a medieval safeguard against poisoning. Melita Historica, 6: 391-406.

Zammit Maempel, G., 1989. The Folklore of Maltese fossils. Papers in Mediterranean Social Studies, 1: 1-29.

Spot the reptile

It was only after this photograph was taken and downloaded to my computer than I realized that a vertebrate could be seen sunbathing on one of the Opuntia stems. Can you spot it?

If not, here it is again, highlighted and enlarged:

The name of this reptile is Tarentola mauritanica L. 1758. The species is generally nocturnal, but that clearly hasn't stopped this individual from enjoying a breath of fresh air!

Variations on a theme, Part IV

The most common invasive plant in the Maltese countryside is the Cape Sorrel (Oxalis pes-caprae L.). The pictures below, taken at Għajn Tuffieħa, show the usual variety of the flower (1), together with another less frequent form exhibiting extra petals (2) resulting from additional sets of chromosomes in the cells' nucleus (polyploidy).

It is known for its sour taste resulting from a reserve of oxalic acid in the plant tissues, which has also resulted in its Maltese vernacular name of Qarsu (=sour).

(1)

(2)

Rats!

One of the commonest rodents in Malta, and the islands surrounding it, is the black rat Rattus rattus (L., 1758). It is usually found living together with man in highly artificial habitats all around the world, but has spread to any area where the temperature is warm enough and where food is in plentiful supply. Since this species is an omnivore (eats both vegetable and animal material), it also creates problematic issues when introduced in areas of ecological uniqueness.

In Malta this problem is seen in mostly relation to the unique reptilian fauna - on the islands of Selmunett, predatory actions of Rattus sp. are the main factors involved in the virtual extinction of the lizard Podarcis filfolensis kieselbachi (Fejervary, 1924), while the introduction of rats on General's Rock may result in the same situation with the lizard Podarcis filfolensis generalensis (Gulia, 1914) (cf. Sciberras & Schembri, 2008; Borg & Sultana, 2003).

The following black rat skulls have been found in Holocene deposits in Buskett and Mistra respectively. The other rat found in the Maltese Islands is the brown rat Rattus norvegicus (Berkenhout, 1769) which, despite its common name, can look highly similar to the black rat in form and colouration.

Examination of the skull, however, makes identification easier.

Black rat Rattus rattus (L., 1798) - specimens from Buskett (left) and Mistra (right). Top photo shows dorsal aspect of the skull, while the bottom photo shows the ventral aspect.

The black rat skull (as can be seen above) has a markedly pointed posterior end, whereas the brown rat's is more rounded. This feature is seen marked with a '1' in the drawings below. In addition, the bony ridges above the eyes also display a distinct difference. They are curved in the skull of the black rat while almost straight in the brown rat's. This feature is seen marked with a '2' in the drawings below. Both drawings are taken from the very interesting paper by Yiğit et al. (1998).

Black rat Rattus rattus (L. 1758) skull drawing

Brown rat Rattus norvegicus (Berkenhout, 1769) skull drawing

References:

Borg, J. J. & Sultana, J., 2003. The presence of the black rat Rattus rattus on Fungus Rock (Maltese islands). The Central Mediterranean Naturalist, 4 (1): 105-106.

Sciberras, A. & Schembri, P. J., 2008. Conservation status of St Paul's Island Wall Lizard (Podarcis filfolensis kieselbachi). Herpetological Bullettin, 105: 28-34.

Yiğit, N., Çolak, E., Sözen, M. & Özkurt, Ş., 1998. The taxonomy and karyology of Rattus norvegicus (Berkenhout, 1769) and Rattus rattus (Linnaeus, 1758) (Rodentia: Muridae) in Turkey. Turkish Journal of Zoology, 22: 203-212.

The 'Scutella Bed'

Specimen of Scutella subrotunda (Leske, 1778) from the British Natural History Museum, E16593

Leske's original description of the sea-urchin Scutella subrotunda, 1778

The rocks of the Maltese Islands formed beneath the sea in the period spanning from the late Oligocene to the late Miocene, from 28 to 5 million years ago.

By looking at the rocks and the fossils they contain, it is possible to deduce which kind of environment existed all those years ago, by comparing them to present marine habitats and environments.

The Lower Coralline Limestone (known in Maltese as Żonqor) is the first exposed rock of the islands. It was the first to form, 28 to 23 millions of years ago, in the Oligocene period.

Towards the end of the Oligocene, the consistency of the Lower Coralline Limestone changed considerably, passing from frequently semi-crystalline, very compact rock (Attard member) to about ten metres' thickness of relatively less rigid, coarser rock (Il-Mara member), with cross-bedding characteristics. This probably represents very suddenly shallowing water, and may suggest tectonic activity.

This changed environment meant that the seabed was now subjected to stronger currents than before, therefore waves would drag large amounts of debris from deeper waters and deposit them onto these shallow reef-like platforms nowadays called the Maltese Islands.

This debris consisted mostly of organisms and their skeletons, the most common of which was the now extinct sea-urchin Scutella subrotunda (Leske, 1778). The large calcium carbonate testas (usually fragmented, but not exclusively) of huge populations of this echinoid compose one or more layers (up to five) marking the end of the Lower Coralline Limestone phase, to the extent that they have been named 'Scutella Beds' by the British geologist T. A. B. Spratt.

Scutella Bed in Xlendi member Lower Coralline Limestone, Spinola Bay

Scutella fossil in Xlendi member Lower Coralline Limestone, Dwejra (Gozo)

References:

Leske, N. G., 1778. Additamenta ad Jacobi Theodori Klein naturalem dispositionem Echinodermatum et lucubratiunculam de aculeis echinorum marinorum. Lipsiae, Leipzig, 278 pp.
Smith, A. B. (ed.), 2005. The Echinoid Directory. [WWW document, link: http://www.nhm.ac.uk/research-curation/projects/echinoid-directory/index; last accessed: 24.V.2010]
Spratt, T. A. B., 1843. On the geology of the Maltese Islands. Proceedings of the Geological Society of London, 4 (2): 225-231.
Spratt, T. A. B., 1854. On the geology of Malta and Gozo [2nd edition]. Malta, 16 pp.

Some views of Ramla l-Ħamra, N Gozo

Two parasitic plants

Parasitic flowering plants are few and far in between. However, two particular genera have been very successful in Mediterranean climates, and both are also represented in the Maltese islands.

The first of these is Cuscuta, which attacks the stems and leaves of other plants - having no roots of its own, this plant entwines itself around other species and sucks nourishment out of their vascular tissues. Its appearance is that of reddish threads interrupted by dense groups of very small white flowers. There are three species of Cuscuta in Malta.

Cuscuta epithymum L. - Magħlaq, 2008. Host - Scilla sp.

The other relevant genus is Orobanche. In contrast to Cuscuta, these parasites attack the roots of other plants. In Malta, one of the commonest species is Orobanche crenata Forsskål, which is very well-known to farmers since it generally attacks legumes (such as broad beans, as in the picture below) and diminishes crop yield.

Orobanche crenata Forsskål - Żejtun, 2009. Host - Vicia faba L.

It may also adapt to parasitism on other plants like Nasturtium, as can be seen in the following picture, taken in St. George's Square at Valletta.

Orobanche crenata Forsskål - Valletta, 2010. Host - Tropaeolum sp.

I would like to thank Dr. S. Lanfranco for confirming the identity of the second Orobanche specimen.

On some fossil brachiopods from the Maltese Islands

Brachiopods are filter-feeders usually indicating seabeds densely populated with algae. The calcium carbonate shell of these animals is fragile and therefore sufficient shelter from waves is usually needed. In fact, they are mostly found in the Upper and Lower Coralline limestones.

The Il-Mâra Lower Coralline Limestone in the north-east areas of Malta occasionally contains populations of a dwarf form of Terebratula vitrea (von Born, 1778). These fragile brachiopods are usually found in association with cidaroid sea-urchin fragments and large species of foraminifers, including Heterostegina.

Terebratula vitrea (von Born, 1778)

In the westernmost parts of Malta, conspicuous 10 to 20cm thick layers of brachiopod shells are often present in cliff faces composed of the Mtarfa Upper Coralline Limestone, amongst rhodoliths and bryozoan fragments. These fossils are often crushed and identification is difficult unless the shell is broken open. Material from these brachiopod layers was used by Cooper (1983) to describe a new genus and species both named for the type locality, namely Maltaia maltensis Cooper, 1983, considered by other writers (Gaetani & Saccà, 1983) to be a synonym of Terebratula sinuosa (Brocchi, 1814). The latter is also found in considerable numbers in the same strata. However, the former species is markedly different in form and is also found in areas where ‘normal’ T. sinuosa is absent .

Terebratula sinuosa (Brocchi, 1814) (lower picture - detail)

Maltaia maltensis (Cooper, 1983) (detail)

The small (6mm) Megathiris detruncata (Gmelin, 1790) and other small species like Argyrotheca sp. are also very common throughout some parts of the Upper Coralline Limestone Formation.

Megathiris detruncata (Gmelin, 1790)

Deep sea such as that in which the Globigerina Limestone formed also offers protection from strong currents that may damage brachiopods. Despite this, brachiopods in this layer are few and far in between. Disarticulated phosphatised valves of the still-extant Megerlia truncata (Linné, 1767) are infrequently found in the C2 Phosphorite Conglomerate Bed.

Megerlia truncata (Linné, 1767)

References:

Cooper, G. A., 1983. The Terebratulacea (Brachiopoda), Triassic to Recent: a study of the brachidia (loops). Smithsonian Contributions to Paleobiology, 50: 1-445.
Emig, C. C., 2006. Brachiopoda world database. [www document, url: http://www.marinespecies.org/brachiopoda, last accessed: 10.II.2010]
Gaetani, M. & Saccà, D., 1983. Brachiopodi neogenici e pleistocenici della provincia di Messina e della Calabria meridionale. Geologica Romana, 22: 1-42.

Yet another cold-blooded encounter

The elegant and perfectly camouflaged Telescopus fallax (Fleischmann, 1831) basks in the late afternoon sun on garigue close to Baħrija, Malta.

Apart from the characteristic patches on its skin, the easiest way to distinguish this species is from its slit-like pupils, similar to those of cats, earning it the common English name of 'cat snake'. All other snake species of the Maltese islands have round pupils.