Naesiotus steadmani Chambers, 1986

CLASSE: GASTROPODA: TERRESTRE

FAMÍLIA: BULIMULIDAE

ESPÉCIE: Naesiotus steadmani Chambers, 1986

Tamanho médio: 12 – 13 mm

Ocorrência: Equador, Arquipélago de Galápagos, Ilha de Santa Cruz

Localidade tipo: Equador, Galápagos, Ilha de Santa Cruz, “Cueva de Kubler” (Excavation Iie, 1.5 Km N Of Puerto Ayora, Large lava tube)

Nome original: Naesiotus steadmani Chambers, 1986

Etimologia: o nome da espécie é uma homenagem ao Dr. David W. Steadman (1951 – ), pioneiro no estudo da fauna terrestre fóssil de Galápagos

Comentários: Segundo Chambers, 1986: “as descrições presentes são baseadas apenas em material de concha; nem espécimes vivos nem partes moles preservadas são conhecidas pelo autor. Há evidências de declínios recentes e provável extinção em caracóis terrestres de Galápagos, então é possível que ambas as espécies recentemente descritas já estejam extintas.”

Descrição original:

(Chambers, 1986): ” Shell conical, consisting of up to 7 whorls, narrowly umbilicate to rimate, reaching 11.8-13.3 mm in height and 6.3-7 mm in width, with proportion of width to height ranging from 0.5 to 0.54 and sides convex in outline. Protoconch consisting of 1.75-2 whorls, with sculpture of fine undulating and anastomosing axial riblets and extremely fine spiral threads. Postembryonic whorls convex and with fine, slightly sigmoid or undulating axial ribs and very fine spiral threads on the first 1.75-2.5 postembryonic whorls, forming small beads at intersections with axial ribs. Sutures weakly impressed. Axial sculpture becoming increasingly more pronounced on body whorl, forming coarse, irregular folds within % turn of
the aperture.

Base of body whorl flattened, making the shell outline somewhat fusiform. Aperture ovate-lunate, somewhat narrowed by flattened parietal wall. When viewed from side, peristome straight, its plane forming an angle of about 30° with axis of shell. Columellar margin reflected and continuous with a thick parietal callus, basal and palatal margins simple or slightly thickened. Parietal lamella 1-2 mm in length and directed toward midpoint of the outer lip and recessed about 3 mm from outermost extent of peristome. Columellar lamella thicker and not as high as parietal lamella and usually extending to the peristome. Palatal thickening extending to edge of peristome. Shell light brown, sometimes with pale spiral band down middle of body whorl, with peristome white.”

Fotos: cortesia Femorale, 2024, 12.7mm

Figura: Chambers, 1986: duas vistas (A e B) do material de Naesiotus steadmani. À esquerda, o HOLOTYPE, seguidos por 03 PARATYPES. À direita USNM 842297, coletado na Cueva de Kubler. Barra da escala = 10 mm

Fontes:

Descrição original: Chambers, S. M. (1986). Two new bulimulid land snail species from Isla Santa Cruz, Galápagos Islands. The Veliger. 28(3): 287-293, figs. 1-3., disponível online em https://www.biodiversitylibrary.org/page/42480411
página(s): 287-289, fig. 1

Chambers, S. M. & Steadman, D. W. (1988). Holocene terrestrial gastropod faunas from Isla Santa Cruz and Isla Floreana, Galápagos: evidence for late Holocene declines. Transactions of the San Diego Society of Natural History. 21(6): 89-110, figs. 1, 2A-L, 3., disponível online em https://www.biodiversitylibrary.org/page/4287005
página(s): 101

Breure, A. S. H. & Borrero, F. J. (2008). An annotated checklist of the land snail family Orthalicidae (Gastropoda: Pulmonata: Orthalicoidea) in Ecuador, with notes on the distribution of the mainland species. Zootaxa. 1768: 1-40., disponível online em https://www.biotaxa.org/Zootaxa/article/view/zootaxa.1768.1.1
página(s): 17

MolluscaBase: https://www.molluscabase.org/aphia.php?p=taxdetails&id=1625938