Partially fossilised shark tooth find

Mr Roy Clarke of East London kindly presented a shark tooth to the museum for identification. It was found along the Cefane beach (Chintsa Bay) recently.

A close inspection of the specimen revealed that the tooth has started to fossilise (discolouration as one indicator) and was imbedded in some lithified coastal sandstone – not an uncommon geological feature in the area.

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A 22-mm-tall fossilised great white shark tooth found by Roy Clarke. Photo: Kevin Cole

A comparison of the tooth shape and dimension assisted in the identification as that belonging to a Great White shark Carcharodon carcharias. Retired museum colleague Greg Brett was able to demonstrate the difference in the tooth shape of other shark species such as the tiger and raggie to name a few in confirming the identification. Distinctive here is the very equal (triangular) presentation of the 2.2 cm tall tooth.

The earliest known fossils of great white sharks are from the mid-Miocene period 16 million years ago.

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Super blue blood moon tomorrow night

The full moon will be in perigee position (closest pass to the Earth) tomorrow evening (known as a supermoon) and being the second supermoon in a month (also called a blue moon) combined with a celestial lunar eclipse (blood moon) all happening to combine in a special event. The last super blood moon event (no blue moon) in East London occurred under cloudy skies on the 28th September 2015.

In the perigee moon position the moon will be 23 506 km’s closer to the Earth at 358 994 km’s than its average distance of 382 500 km’s. This usually translates on a clear evening to the moon appearing to look 14% larger than normal and 30% brighter.

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Full moon rising over Beacon Bay, East London. Photo: Kevin Cole

Unfortunately we will not be able to experience the eclipse in our part of the world. However, the supermoon spectacle should be worth a look up starting at 19h20 tomorrow evening (moonrise).

Although there have been a number of supermoons and lunar eclipses the astronomical trifecta of a blood moon as well is most unusual.

There will be a super blue moon event later in the year on the 31 March 2018 and a total lunar eclipse visible on the 27/28th July 2018. Two super blue moons in a year is also a rare event.

Beach swimmers should be wary of the spring tide at this time and anglers should also take special precautions not to be caught unawares on the rocks. The higher than normal tides will also result in stronger rip currents.

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Furry little Otomys visitor

Untamed indigenous gardens have some special benefits as was revealed at a home in Beacon Bay on the 1st December 2017. An adult vlei rat, Otomys irroratus, followed a clearly marked run from its saucer-shaped nest to an open feeding area of grass. It was shortly followed by a pair of youngsters who cautiously started feeding close by.

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Ten species of the genus Otomys occur in Africa and O. irroratus is illustrated here. Photos: Kevin Cole                      

Vlei rats are wholly herbivorous and their digestive tract shows some advanced specialisation. The feeding trait is illustrated above where the  plant material was bitten off at the stem by the adult and then picked up in the mouth and grasped on either side by the paws and short 20-50 mm pieces cut off and chewed. Also noticeable is that this individual is sitting in a semi-upright position on its haunches while feeding. They are anti-social animals and tend towards isolation in adulthood.

Unlike other rat species only two or three precocial young are born at a time with their incisors slightly erupted (so as not to cause too much discomfort to the female while suckling).

Snakes and owls prey on the species  and in Beacon Bay mongooses and genets (large-spotted)  would also find them a tasty food source.

References:

The rodents of southern Africa by G De Graaff

The mammals of the southern African subregion by JD Skinner and RHN Smithers

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A ‘lynx’ that can cling to a wall …. .

A week ago a strange looking spider was observed maneuvering up a wall at home in Beacon Bay, East London. It was small in size with large spiny bristles on the legs. It responded quite quickly to human movement and moved swiftly up the wall.

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A lynx spider of the genus Oxyopes                                                                        Photo: Kevin Cole ELM

Intrigued and unable to identify the spider I contacted Astri Leroy of the Spider Club of South Africa (info@spiderclub.co.za). She quickly responded with the following reply ‘It’s a male (see the hugely modified ends to his palps, like little boxing gloves)  small lynx spider, of the family Oxyopidae, in the genus Oxyopes.  There are a number of species in this genus that are common, widespread and very difficult to separate into species from photos.  In fact as far as I can recall just under 30 different species in the genus’.

Reading up on these spiders it is further revealed that they do not build a web, are not known to be harmful to humans and are found on flowers, leaves, grasses and occasionally come indoors. The numerous spines stand out at right angles to the legs and some of the species can be very brightly coloured.

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Note the spiny bristles on the legs and ‘boxing glove’ like palps on this lynx spider                            Photo: Kevin Cole ELM

A behavioural trait of stalking and jumping at prey like a cat probably gives rise to their common name – the lynx spider. They have been known to jump 2 cm in the air to seize a passing insect in full flight.

References:

Spiders of southern Africa by Astri and John Leroy

Southern African spiders: An identification guide by Martin R. Filmer

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Bronze plaque from the Grosvenor (1782) shipwreck site

Mr Philip Vorster from Mboyti along the Wild Coast kindly donated a bronze plaque which reflects the history of the first steam engine to be used during a salvage attempt of the Grosvenor in 1887.

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The steam engine was manufactured by Robey and Company in Lincoln (UK). Mr Bryan Edwards of the Robey Trust kindly provided the following information related to the number 9987 on the plaque:

“9987 is an entry in Engine Book 2, and as such the details are more brief than they were in EB3 onwards.  All we have is that:

9987 was a 12hp, compound (would almost certainly have been a 2-cylinder) ….

Machinery Order number  4260.

Delivery:  19-10-1887″

The steam engine was landed in Durban and transported overland by wagon to the Grosvenor wreck site.

The museum has a permanent display about the Grosvenor in the maritime gallery.

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Nahoon Beach – storm surge event

Nature is proving the hypothesis that increased annual storm surges will be experienced along the South African coastline in years to come. The museum has recorded events over the past two decades and it has been noted that apart from big storm surges every few years (the last being in 2015) mini storm surges are increasing annually.

The biggest annual event occurred last night and a photographic record from Nahoon Beach illustrates just how large the impact was on the coastal primary dune adjacent to the internationally known beach.

A spring tide and days of windy coastal conditions (probably from storm centers south of the SA coast) produced heavy seas with large high energy waves displacing onto the shoreline. Areas where these waves were focused by a bay or promontory (such as Nahoon Point) received a battering and, in particular, the primary dune at Nahoon Beach.

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In recent times there has been no embryonic dune formation with concomitant stabilisation by pioneering dune plants and the effects of these waves erodes directly at the base of the primary dune. The caused massive dune slumping with tons of sand being eroded out to be deposited elsewhere.

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A hint of what was to come was noted on Monday 21st August 2017 when museum scientist Kevin Cole visited Nahoon Beach to document the beginning of an erosive coastal event. It was noted that concrete plinths used to stabilise a sewer connector pipeline had been exposed (for the first time in decades) indicating a low base erosion event along the beach.

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The dune slumping which had occurred along the primary dune at Nahoon Beach was not higher than 3m (as illustrated by the two ladies standing in the photo below taken on Monday 21st August 2017).

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The storm surge last night and this morning has further eroded the dune system, almost to the vegetation line (illustrated below- top photo Monday 21st August 2017, bottom photo Thursday 24th August 2017).

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Additional concrete plinth bases have also been exposed which run a line to the Nahoon River mouth. At the mouth on a very low tide the remains of the sewer pipe can be seen (in part) under the water crossing the river.

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As expected some other interesting specimens which have been buried will be found. A case in point is that a young visitor from KwaZulu-Natal found an animal tooth (which still has to be identified) at the Nahoon corner car park this morning.

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A site visit will be made to Nahoon tomorrow as more dune erosion is expected to take place at high tide later today and tomorrow morning.

 

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There is a dwarf in the tree ….

A few nights back an Eastern Cape Dwarf chameleon (Bradypodion ventrale) was spotted in an acacia tree in Beacon Bay, East London. Many years ago this species were quite common but they haven’t been seen regularly in recent times.

The Eastern Cape Dwarf chameleon is one of the larger of the fifteen currently recognised species of dwarf chameleons in South Africa (all of which are endemic to the country). The genus is widespread but essentially absent from the Kalahari and the Karoo.

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Eastern Cape Dwarf chameleon in Beacon Bay. Photo: Kevin Cole ELM

All dwarf chameleons are viviparous – an average of 5-15 babies are born alive and fully developed after a gestation period of about 3 months. These tiny (20mm) reptiles are fully equipped for survival and can feed on small insects.

Bradypodion ventrale illustrated above can be identified by a casque that is slightly swept back, a pale gular region and a dorsal crest composed of pronounced triangular tubercles. Two rows of larger tubercles are also noted on the flanks. It is a grey chameleon with a light central patch on the flanks. The enlarged tubercles my be yellow or green to orange-brown.

Chameleons are not found worldwide – restricted to Madagascar, Africa and some neigbouring islands such as the Comores, Mauritius, Seychelles and Zanzibar. There are about 150 – 160 species arranged into 9 genera.

Reference: Chameleons of southern Africa by Krystal Tolley and Marius Burger

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