Tag Archives: British Overseas Territory

Isotornus aterrimus Wollaston

Black Saint Helena Weevil (Isotornus aterrimus)   

The Black Saint Helena Weevil was described in 1877, it was endemic to the island of Saint Helena in the southern Atlantic Ocean.  

The species was adapted to a single food plant, the endemic Boxwood (Mellissia begoniifolia (Roxb.) Hook. f.), a highly threatened shrubby species that was even extinct in the wild.  

T. V. Wollaston, the author of the species writes in 1877.:  

The present Isotornus is due to the researches of Mr. P. Whitehead, who has lately communicated to me an interesting series of examples which he captured, within the dead wood of the Mellissia begoniaefolia (or native “Boxwood”), on Rock-Rose Hill.” [1]  

***  

The species was not found during intensive field searches in 1965/66 and 2005/06 and is most probably extinct.  

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References:  

[1] T. Vernon Wollaston: Coleoptera Sanctae-Helenae. London: John Van Voorst, Paternoster Row 1877 
[2] Howard Mendel; Philip Ashmole; Myrtle Ashmole: Invertebrates of the Central Peaks and Peak Dale, St. Helena. Report for the St Helena National Trust, Jamestown 2008  

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edited: 02.12.2018

Bembidion fossor (Wollaston)

Digging Bembidion Ground Beetle (Bembidion fossor)  

The Digging Bembidion Ground Beetle seems to have been on the edge of extinction already in the 19th century.  

See Thomas Vernon Wollaston in the year 1877 (Coleoptera Sanctae-Helenae).:  

With the exception of the B. evanescens, this is the smallest of the St.-Helena Bembidia; and it is perhaps the rarest of the whole of them, being hitherto unique. My example was taken by myself from the interior of the decayed stem of a tree fern, which I had brought away for after-examination from the vicinity of Diana’s Peak.”  

***

The most recent searches in the years 2005 to 2006 failed to find any trace of this species.  

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References:  

[1] T. V. Wollaston: Coleoptera Sanctae-Helenae. London: John Van Voorst, Paternoster Row 1877 
[2] H. Mendel; P. Ashmole; M. Ashmole: Invertebrates of the Central Peaks and Peak Dale, St Helena. 2008  

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Photo: The Trustees of the Natural History Museum, London

(under creative commons license (4.0))
https://creativecommons.org/licenses/by/4.0/

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edited: 30.05.2021

Anthicodes maculatus Wollaston

Spotted Ant-like Beetle (Anthicodes maculatus)

The genus Anthicodes currently contains about eight species, of which two (Anthicodes fragilis Woll. and Anthicodes maculatus) were found on the island of Saint Helena. Thomas Vernon Wollaston wrote about the Saint Helena spotted flower beetle in 1877 (Coleoptera Sanctae-Helenae).:  

The first spot in which I met with this robust and singular Anthicid is the Aster-grove [Commidendrum robustum ssp. gummiferum (Roxb.) Cronk] beyond West Lodge, on the inner slope of the great Sandy-Bay crater and overlooking Lufkins; and it was not until after the early summer rains, about the end of January, that it began to make its appearance more abundantly. At that time, however, it was found by Mrs. Wollaston and myself in comparative profusion, – at the edge of the tremendous precipice immediately above West Lodge, adhering to small pieces of stick which were lying on the exposed rocky soil, as well as on the only available portion of the almost inaccessible ground behind High Peak.”  

***

The species is most likely extinct today, as it could not be detected during any of the surveys of the last few years in its former range. 

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References:  

[1] T. Vernon Wollaston: Coleoptera Sanctae-Helenae. London: John Van Voorst, Paternoster Row 1877

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edited: 07.05.2021

Commidendrum robustum ssp. gummiferum (Roxb.) Cronk

Saint Helena Gumwood (Commidendrum robustum ssp. gummiferum)  

The genus Commidendron consists of only four species, all of which are restricted to the island of Saint Helena.  

The 7 to 8 m tall Saint Helena Gumwood (Commidendrum robustum (Roxb.) DC.) is Saint Helena’s national tree and probably was once by far the most abundant tree on the island.  

The species can be split into two subspecies, of which the ssp. gummiferus is extinct today. However, there remains a population of hybrids at Peak Dale in the island’s southwestern center, in which this subspecies is at least genetically contained. The time of its extinction seems to be unknown.  

… but of course the reasons ….  

T. Cavendish in his report about the island (The Prosperous Voyage of M. Thomas Candish esquire into the South Sea, and so around about the circumference of the whole earth, begun in the yere 1586, and finished 1588.) wrotes:  

There are in this yland thousands of goates, which the Spaniards call Cabritos, which are very wilde: you shall see one or two hundred of them together, and sometimes you may beholde them going in a flocke almost a mile long. Some of them, (whether it be the nature of the breed of them, or of the country I wot not), are as big as an asse, with a maine like an horse and a beard hanging downe to the very ground: they will clime up the cliffes which are so steepe that a man would thinke it a thing unpossible for any living thing to goe there. We tooke and killed many of them for all their swiftnes: for there be thousands of them upon the mountaines.”  

Those trees, that escaped the goats’ appetite, were later cut down for fire wood.  

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References:  

[1] Q. C. B. Cronk: The decline of the St Helena gumwood Commidendrum robustum. Biological Conservation Vol. 35(2): 173-186. 1986  

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nominate race  

Depiction from: ‘John Charles Meliss: St. Helena: A Physical, Historical, and Topographical Description of the Island, including its Geology, Fauna, Flora, and Meteorology. London: L. Reeve & Co. 1875’  

(public domain)

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edited: 21.03.2018

Nesiobius barbatus (Wollaston)

Bearded Nesiobius Weevil (Nesiobius barbatus)  

The Bearded Nesiobius Weevil was described in the year 1877 by T. V. Wollaston on the basis of just three specimens, that he had collected by himself at a difficult to access slope at High Peak on the island of Saint Helena.:  

The only three examples which I have yet seen of this very rare Nesiotes were taken by myself on a precipitous and barely accessible slope behind High Peak and overlooking Peak Gut; and, in conjunction with the N. fimbriatus from Thompson’s Wood, it possesses a peculiar interest through the fact of its scape being powerfully barbed towards the inner apex with a cluster of coarse, elongated, squamiform bristles. This latter character, which is only faintly traceable in some of the other members of the group (and which, indeed, in the N. squamosus and simplex appears to be altogether absent), is so conspicuous in the barbatus and fimbriatus that, when taken in connexion with heir minute but very prominent eyes, the stronger and more erect setae of their entire surface, and their anteriorly much constricted prothorax, it is sufficient to place them in a different section of the genus ….” [1]

***

The species inhabited the forests dominated by the endemic Bastard Gumwood (Commidendrum rotundifolium(Roxb.) DC.), a tree species that is now completely extinct; the beetle was not fund during the recent field searches and is very likely extinct. [2]  

***

The depiction below shows the Scaled Nesiobius Weevil (Nesiobius squamosus (Wollaston)); one of the still extant species of the genus. 

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References:  

[1] T. Vernon Wollaston: Coleoptera Sanctae-Helenae. London: John Van Voorst, Paternoster Row 1877 
[2] Howard Mendel; Philip Ashmole; Myrtle Ashmole: Invertebrates of the Central Peaks and Peak Dale, St Helena. 2008  

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Scaled Nesiobius Weevil (Nesiobius squamosus (Wollaston))  

Depiction from: ‚T. Vernon Wollaston: Coleoptera Sanctae-Helenae. London: John Van Voorst, Paternoster Row 1877‘  

(public domain)

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edited: 29.05.2021

Ingolfiella longipes Stock, Sket & Iliffe

Long-legged Ingolfiella Amphipod (Ingolfiella longipes)

This species was described in 1987; it is still known only from a single specimen that was collected from Walsingham Sink Cave, an anchialine cave in Hamilton Parish, Bermuda Islands.

The species has never been found since and (even if rather unlikely) might be extinct.

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edited: 14.08.2022

Poecilozonites reinianus (Pfeiffer)

Flat Bermuda Land Snail (Poecilozonites reinianus)

The Flat Bermuda Land Snail was described in 1864, it is one of 12 species that are known from the Bermuda Islands.

The species is known apparently from fossil- as well as from recent specimens, but appears to be already extinct now. 

The shells reached sizes of about 0,3 cm in heigth and about 1 cm in diameter.

Unfortunately I cannot say much about this species, the same applies to all congeneric species of snails from the Bermuda Islands.

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References:

[1] Henry A. Pilsbry: Recent and fossil Bermudan snails of the genus Poecilozonites. Proceedings of the Academy of Natural Sciences of Philadelphia 76: 1-9. 1924

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Depiction from: ‘H. A. Pilsbry: On the helicoid land molluscs of Bermuda. Proceedings of the Academy of Natural Sciences of Philadelphia 40: 285-291. 1888’

(public domain)

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edited: 11.05.2019

Tychiorhinus inaequalis Wollaston

Unequal Saint Helena Weevil (Tychiorhinus inaequalis)

The Unequal Saint Helena Weevil was described in 1877; it is, or probably was, restricted to the island of Saint Helena.

The species appears to have already been on the brink of extinction when it was discovered.:

Although of extreme rarity, I have nevertheless taken the T. inaequalis in widely distant parts of the great central ridge (to which it seems to be peculiar), – namely amongst the sticks and wood of the old cabbage-trees about Diana’s Peak and Actaeon, as well as (under similar circumstances) at Cason’s, and at the edge of the precipice, or crater-wall, immediately above West Lodge.” [1]

***

The Unequal Saint Helena Weevil was not found during the most recent field surveys and is now feared to be extinct.

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References:

[1] T. Vernon Wollaston: Coleoptera Sanctae-Helenae. London: John Van Voorst, Paternoster Row 1877

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edited: 26.05.2021

Bidens hendersonensis var. oenoensis Sherff

Oeno Island Beggartick (Bidens hendersonensis var. oenoensis)

The Henderson Island Beggartick is found on Henderson Island, Pitcairn Islands and also occurs or occurred on the nearby Oeno Atoll, some three variaties are sometimes distinguished, with the form from the Oeno Atoll being one of them.

The Oeno form was only collected once in 1991, and was probably last seen in 1997. 

***

The Oeno Island Beggartick is now sometimes treated as a synonym of the nominate form, I’ll mention it here just for the sake of completeness. 

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edited: 18.06.2019

Prosadenoporus agricola (Willemoes-Suhm)

Bermudas Terrestrial Smiling Worm (Prosadenoporus agricola 

The Bermudas Terrestrial Smiling Worm was described in 1874, it was restricted to the Bermudas Islands.

The milky-white, brownish or greenish colored species was commonly found along the shores of mangrove swamps, under stones and logs on moist, silty soil or inside earthworm burrows above the high-water mark and, during the wet season, also on adjacent hillsides.

The former habitat of this species is now completely lost due to commercial development.
Some very few last survivors – the last of their kind – were found during intensive field searches in 1966, since then the species is considered extinct. [1]

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Depiction from: ‘A. E. Verrill: The Bermuda islands: an account of their scenery, climate, productions, physiography, natural history and geology, with sketches of their discovery and early history, and the changes in their flora and fauna due to man. New Haven, Conn.: the author 1902’

(public domain)

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References:  

[1] Svetlana A. Maslakova; Jon L. Norenburg: Revision of the smiling worms, genera Prosadenoporus Burger, 1890 and Pantinonemertes Moore and Gibson, 1981 and description of a new species Prosadenoporus floridensis sp. nov. (Prosorhochmidae; Hoplonemertea; Nemertea) from Florida and Belize. Journal of Natural History 42: 25-26. 2008

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edited: 03.11.2020

Helenoconcha sexdentata (Smith)

Six-toothed Saint Helena Snail (Helenoconcha sexdentata)  

The Six-toothed Saint Helena Snail was described in 1893, as its name implies, it is, or rather was, endemic to the island of saint Helena.

This species agrees rather closely with P. pseustes, Smith, in respect of the dentition of the aperture. The palatal lamella, however, in that species is considerably stronger, and the form of the shell is very different. P. cutteri has two similar parietal lamellae, only two basal denticles, and no palatal lamella. In other respects it appears to be very similar, but a trifle larger. Watercresses (Nasturtium officinale) among which it is stated by M. Eudel [M. Emile Eudel, the collector of this species] that this species occurs, are said to be “very common in the ravines and along the mountain streams and ponds.”.” [1]

The shells reach sizes of about 0,3 cm in diameter. 

***

The Six-toothed Saint Helena Snail was apparently still found alive when it was described; it is nevertheless now considered extinct. [1]

***

The species of this genus, as well as basically all of the Saint Helena Gastropoda species, are in urgent need of a proper revision!

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References:

Edgar A. Smith: Descriptions of two new species of Patula from St. Helena. The Conchologist 2(7): 164-165. 1893

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Depiction from: ‘Edgar A. Smith: Descriptions of two new species of Patula from St. Helena. The Conchologist 2(7): 164-165. 1893’

(public domain)

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edited: 29.05.2021

Bembidion sublimbatus Wollaston

Bordered Bembidion Ground Beetle (Bembidion sublimbatus 

The Bordered Bembidion Ground Beetle, described in 1877, was obviously restricted to a very small area at the Central High Ridge in the center of Saint Helena, where the species appears to have already been rare when it was first discovered.  

Thomas Vernon Wollaston wrote about it in 1877 (Coleoptera Sanctae-Helenae).:  

The only spot in which I have met with this extremely rare Bembidium is towards the western extremity of the great central ridge, immediately above the house known as West Lodge, – where, early in February, I took it, on two or three occasions, at the very edge of the tremendous precipice which overlooks the Sandy-Bay crater. It was found beneath damp wood, leaves, and sticks, amongst shrubs of the Aster gummiferus [Commidendrum robustum ssp. gummiferum (Roxb.) Cronk] and common gorse; and, although it may perhaps be more plentiful on the perfectly inaccessible Aster-clothed slopes below (extending from thence to High Peak), my utmost endeavours enabled me to secure only eight or nine specimens; though as both sexes are well represented, this is more than sufficient for all practical purposes.”  

***

The most recent field searches in 2008 found the type locality of the species being more or less completely eroded, yet did not produce any trace of the beetle itself, which is thus feared to be extinct.  

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References:  

[1] T. V. Wollaston: Coleoptera Sanctae-Helenae. London: John Van Voorst, Paternoster Row 1877 
[2] H. Mendel; P. Ashmole; M. Ashmole: Invertebrates of the Central Peaks and Peak Dale, St Helena. 2008

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Photo: The Trustees of the Natural History Museum, London

(under creative commons license (4.0))
https://creativecommons.org/licenses/by/4.0/

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edited: 30.05.2021

Chilonopsis helena (Quoy & Gaimard)

Saint Helena Awl Snail (Chilonopsis helena 

The Saint Helena Awl Snail was described in the year 1833 based on subfossil shells.  

***

Thomas Vernon Wollaston writes in the year 1878 (Testacea Atlantica).:  

The present Bulimus, which was admirably figured by Quoy in 1833, occurs rather abundantly on the extreme summit of the Barn, and in that immediate neighbourhood, lying loosely on the surface soil, beneath the shrubs of Salsola, &c., – where it has much the appearance of having lived at a comparatively recent period. At all events many of the examples have their colour and outher cuticle completely preserved, – though it is equally true that the majority of them are decomposed, decorticated, and colourless.” [1]  

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References:  

[1] T. Vernon Wollaston: Testacea Atlantica: or the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. London: L. Reeve & Co. 1878  

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Depiction from: ‘Edgar A. Smith: On the Land-Shells of St. Helena. Proceedings of the Zoological Society of London 258-270. 1892’  

(public domain)

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edited: 21.03.2018

Kerzhneria hirsuta Schmitz

Kerzhner’s Damsel Bug (Kerzhneria hirsuta)

Kerzhner’s Damsel Bug, which is/was endemic to the highly isolated island of Saint Helena in the southern Atlantic Ocean, was described in 1977. [1]

The species was found on Cabbage Tree Road and on High Peak at the central ridge.

Kerzhner’s Damsel Bug reaches a length of only about 0,5 cm, it has an oval abdomen and minute wings and thus appears to be flightless.

The species was not found during the most recent fiels surveys in 2005/06 and may indeed be extinct, yet there is still the chance that it was just overlooked. [2]

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References:

[1] C. P. Alexander; A. M. Hutson; R. W.  Crosskey; R. P. Lane; D. A. Duckhouse; P. Van Schuytbroeck; K. G. V. Smith; P. H. S. Van Doesburg; P. H. J. Van Doesburg: Terrestrial fauna of the island of St Helena. Koninklijk Museum voor Midden Afrika Tervuren Belgie Annalen Zoologische Wetenschappen 215: 1-533. 1977
[2] Howard Mendel; Philip Ashmole; Myrtle Ashmole: Invertebrates of the Central Peaks and Peak Dale, St. Helena. Report for the St Helena National Trust, Jamestown 2008

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edited: 21.06.2020

Pampusana leonpascoi (Worthy & Wragg)

Henderson Island Ground Dove (Pampusana leonpascoi)

The Henderson Island Ground Dove was described in 2003, it was endemic to Henderson Island, Pitcairn Islands.

The species is known exclusively from subfssil remains which indicated that it was a ground-dwelling, flightless bird, it was apparently extirpated by Polynesian settlers who temporarely inhabited Henderson Island.

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edited: 09.03.2020

Amazona sp. ‘Montserrat’

Montserrat Amazon (Amazona sp.)

The Montserrat Amazon is known only from subfossil remains, a coracoid, a femur, two humeri and an ulna, found at the Trants archaeological site on the island of Montserrat.

The species was the smallest member of its genus found in the Caribbean region so far. [1]

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References:

[1] Charles A. Woods; Florence E. Sergile: Biogeography of the West Indies: Patterns and Perspectives, Second Edition. CRC Press; Auflage: Subsequent 2001

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edited: 13.02.2020

Prosobonia sauli De Pietri et al.

Henderon Island Sandpiper (Prosobonia sauli)

The Henderson Island Sandpiper is known from subfossil remains, which were compared to the bones of the extant Tuamotu Sandpiper (Prosobonia parvirostris (Peale)); it differed from that species by its longer leg bones and its reduced outer wing bones.

Given the fact that this species apparently had some reduced flight abilities, it might have indeed been restricted to Henderson Island. [1]

The species was finally described in 2020 as a new species, after having been known for almost 26 years. [2]

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References: 

[1] Graham M. Wragg; Marshall I. Weisler: Extinctions and new records of birds from Henderson Island. Notornis 41: 61-70. 1994 
[2] Vanesa L. De Pietri; Trevor H. Worthy; R. Paul Scofield; Theresa L. Cole; Jamie R. Wood; Kieren J. Mitchell; Alice Cibois; Justin J. F. J. Jansen; Alan J. Cooper; Shaohong Feng; Wanjun Chen; Alan J. D. Tennyson; Graham M. Wragg: A new extinct species of Polynesian sandpiper (Charadriiformes: Scolopacidae: Prosobonia) from Henderson Island, Pitcairn Island Group, and the phylogenetic relationships of Prosobonia. Zoological Journal of the Linnean Society 20: 1-26. 2020

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edited: 07.05.2021

Nycticorax olsoni N. P. Ashmole, K. E. L. Simmons & W. R. P. Bourne

Ascension Island Night-Heron (Nycticorax olsoni)  

This species of night-heron was described in the year 2003 based on subfossil bones, which were found in guano deposits. In live this species was somewhat smaller than the Night-Heron (Nycticorax nycticorax (L.)), and it was most probably a weak flyer but not fully flightless.  

The Ascension Island Night-Heron may have stayed near the coast, where it searched the giant sea bird colonies, existing on the island at that time, for unattended fledglings, resp. fished for crustaceans at the shore.  

The species reached a length of about 50 to 60 cm.  

The circumstances of its extinction are not known, but introduced rats may well have played a role as they did in so many other cases of extinctions of birds on islands.  

***

In chapter 21 (D’une isle nommée l’Ascention.) of his book ‘Les singularitez de la France antarctique, autrement nommée Amérique, et de plusieurs terres et isles découvertes de nostre tems.’ from the year 1557 André Thevet describes a bird from Ascension Island which indeed could well be the Ascension Island Night-Heron.:  

Dauantage en ceste isle s’en trouue une espece de grands, que i’ay ouy nommer Aponars. Ils ont petites ailes, pourquoy ne peuuent voler. Ils sont grands et gros comme noz herons, le ventre blanc, et le dos noir, comme charbon, le bec semblable à celuy d’un cormoran, ou autre corbeau. Quand on les tue ils criênt ainsi que porceaux.”  

translation:  

Furthermore in this Ilande there is a certayne kinde of greate birdes that I have heard called Aponars, they have little wings, and therefore they cannot flye. They are great and hye lyke hearnshawes, the belly white, and the backe blacke as cole, the byll lyke to a cormorant, or a different crow. When they are killed they crye lyke hogs.”  [1]

***

The Ascension Island Night-Heron very likely disappeared shortly after.  

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References:  

[1] A. Thevet: The new found worlde, or Antarctike. London: Henrie Bynneman for Thomas Hacket 1568

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edited: 20.10.2016

Sporobolus durus Brongn.

Ascension Island Dropseed Grass (Sporobolus durus)  

The Ascension Island Dropseed Grass is one of the few native resp. endemic plant species of Ascension Island.  

The species was last recorded in the year 1886 at the White Horse Hill, where it grew at an elevation of about 450 m. This place is now densely covered with the introduced Molasses Grass (Melinis minutiflora P. Beauv.).  

The Ascension Island Dropseed Grass could not be relocated during extensive searches in the year 1998, and it is now considered extinct.  

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Depiction from: ‘M. L. I. Duperrey: Voyage autour du monde: Exécuté par Ordre du Roi, Sur la Corvette de Sa Majesté, La Coquille, pendant les années 1822, 1823, 1824, et 1825, par M. L. I. Duperrey; Botanique, par Mm. d’Urville, Bory de St-Vincent et Ad. Brogniart. Paris: Arthus Bertrand 1828’  

(public domain)

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edited: 18.05.2011

Ducula harrisoni Wragg & Worthy

Henderson Island Imperial-Pigeon (Ducula harrisoni)

This species was described in 2006, it is known from subfossil remains recovered from Henderson Island, Pitcairn Islands, which originally were thought to originate from two different species.

The Henderson Island Imperial-Pigeon was larger than all living members of its genus, it had enlarged leg- and reduced wing elements, so was on its way to become flightless.

The species was apparently among the first birds from Henderson Island to become extinct due to hunting by Polynesian settlers.

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edited: 14.05.2019

Nyhimbricus wollastoni (White)

Wollaston’s Leafhopper (Nyhimbricus wollastoni)  

Wollaston’s Leafhopper, which is/was endemic to the island of Saint Helena in the southern Atlantic Ocean, was described in 1878.  

The species reaches a length of about 0,5 cm, it is distinctly pale yellow colored and bears orange marks on its head and its pronotum as well as orange bands on its forewings.  

The species was not found during intensive searches in recent years and is thus probably already extinct. [1]  

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References:  

[1] Howard Mendel; Philip Ashmole; Myrtle Ashmole: Invertebrates of the Central Peaks and Peak Dale, St. Helena. Report for the St Helena National Trust, Jamestown 2008  

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Photo: Tristan Bantock The Natural History Museum  

(under creative commons license (2.0)) 
http://creativecommons.org/licenses/by-nc/2.0

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edited: 01.12.2018

Chilonopsis nonpareil (Perry)

Large Saint Helena Awl Snail (Chilonopsis nonpareil)  

The Large Saint Helena Awl Snail is the largest member of its genus, some shells reached sizes of up to 4,7 cm.  

***

See Thomas Vernon Wollaston in 1878 (Testacea Atlantica).:  

The B. auris-vulpina, which has been brought from St. Helena by almost every naturalist who has visited the island during the last fifty years, appears to be quite extinct; though the comparatively perfect preservation of occasional examples, in which the outher cuticle is hardly destroyed and even the colour is partially traceable, would perhaps imply that it must have lingered on to a somewhat recent period.” [1]  

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References:  

[1] T. Vernon Wollaston: Testacea Atlantica: or the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. London: L. Reeve & Co. 1878  

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Depiction from: ‘Edgar A. Smith: On the Land-Shells of St. Helena. Proceedings of the Zoological Society of London 258-270. 1892’  

(public domain)

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edited: 21.03.2018

Philonesia pyramidalis Preece

Pyramid-shaped Philonesia Snail (Philonesia pyramidalis 

This species was described in 1998.  

The Pyramid-shaped Philonesia Snail was endemic to Henderson Island, Pitcairn Islands, and is known from only three adult subfossil specimens and some apical fragments.  

The shells on average reached sizes of about 0,9 cm.  

The three known specimens differ in the color banding; thus, the Pyramid-shaped Philonesia Snail is believed to have possibly been polymorphic like some of its congeners.  [1]  

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References:  

[1] R. C. Preece: Impact of early Polynesian occupation on the land snail fauna of Henderson Island, Pitcairn group (South Pacific). Philosophical Transactions of the Royal Society of London B 353: 347-368. 1998  

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edited: 25.10.2017