Plectreurys pittfieldi Penney

Penney, David, 2009, A new spider family record for Hispaniola — a new species of Plectreurys (Araneae: Plectreuridae) in Miocene Dominican amber, Zootaxa 2144, pp. 65-68 : 66-67

Plectreurys pittfieldi Penney , sp. nov.

( Figs. 1–5 )

Diagnosis: Embolus long, with a spatulate tip, and distinctly sickle-shaped with a clearly demarked basal region forming the ‘handle’ of the sickle. This basal region consists of a tight twist, without forming a loop. Tibia 1 with distal, strong retrolateral coupling spur and a long ventral spine just beyond the midpoint; metatarsus 1 with a distinct curvature.

Description: Male holotype ( Figs 1–5 ). Body length not measurable due to poor preservation of abdomen, but was presumably less than 4.0 mm in life. Carapace 1.6 mm long, 0.9 mm wide, with rounded sides. The only other details visible are two contiguous lateral eyes on both sides. The median eyes cannot be resolved due to the poor preservation, but are presumed to have been present in the living animal. Similarly, details of the ventral prosoma (sternum, chelicerae, maxillae, etc.) are unclear and the abdomen is only partially preserved, with no features of note visible other than a fine covering of short setae. Relative order of leg length 1,4,2,3. Leg 1 femur (fe) 2.1 mm, patella+tibia (pa+ti) 3.0 mm, metatarsus (mt) 1.2 mm, tarsus (ta) 1.0 mm, total 7.3 mm; leg 2 fe 1.6 mm, pa+ti 1.6 mm, mt 1.3 mm, ta 0.7 mm, total 5.2 mm; leg 3 fe 1.4 mm, pa+ti 1.2 mm, mt 1.1 mm, ta 0.6 mm, total 4.3 mm; leg 4 fe 1.5 mm, pa+ti 2.2 mm, mt 1.5 mm, ta 0.6 mm, total 5.8 mm. Legs long and slender. True leg spines are difficult to differentiate from normal setae ( Figs 1–2 ), although each femur appears to have at least two dorsal spines. Femur 1 also has three distal, prolateral spines. Tibia 1 with distal, strong retrolateral coupling spur on a distinct base, and a long ventral spine just beyond the midpoint ( Fig. 3 ). There is also one basal prolateral spine and two basal retrolateral spines. The latter appear flattened ( Fig. 3 ) but this is presumably as a result of compression during diagenesis. Metatarsus 1 distinctly curved ( Fig. 3 ). Tarsus with three claws. Paired claws with eleven teeth and unpaired claw with a single basal projection. Pedipalp without modified or enlarged segments, embolus long, with a spatulate tip, and distinctly sickle-shaped with a smooth curve and a clearly demarked basal region forming the ‘handle’ of the sickle. This basal region consists of a tight twist, without forming a loop ( Figs 4–5 ).

Type: Holotype male in Miocene Dominican amber, held in the American Museum of Natural History, New York. Etymology: The specific epithet is after Connor Pittfield, at the request of the collector and donor, Keith Luzzi. Distribution: Miocene Dominican Republic amber forest.

Discussion: This is the first fossil record of an extant plectreurid genus and only the second described fossil of the family. The new species belongs in the tristis species group sensu Gertsch (1958), which is primarily distributed in Mexico and Cuba and is characterized by having longer, thinner legs and a considerably longer palpal embolus than the castanea species group, more common in the USA. Of the twelve species currently assigned to the tristis group, seven are known from both males and females, three from females only and two from juveniles only ( Platnick 2009). In addition, the shape of the palpal bulb in the fossil, although similar in both cases, is quite dissimilar to the sub-spherical bulb present in all but P. zacateca Gertsch , which has a more pear-shaped structure. However, it is highly likely that the bulb in the fossil species has undergone a similar distortion to the rest of the body as a result of the diagenetic processes mentioned above. Thus, determining the relationships of the new fossil species is somewhat difficult. However, considering the shape of the embolus, including the tight basal twist and spatulate tip, P. pittfieldi sp. nov. appears to be most closely related to the Cuban species P. globosa Franganillo , which differs by having the basal twist less tight and in having an additional second twist towards the embolus tip ( Alayón 1993).

Extant Plectreurys are usually found at ground level in arid habitats ( Jiménez 2006), so the discovery of a new species in Dominican amber, which was produced in a moist tropical forest, is somewhat surprising, although the extant Cuban P. globosa is known to favour humid conditions. When the fossil and extant Hispaniolan spider data are combined and compared, the overall pattern is suggestive of a South American origin ( Penney, 2008). However, there will always be exceptions to the rule and it is important to consider origins on a taxon by taxon basis. The available data do not support a South American origin for Hispaniolan Plectreuridae . This family probably reached Hispaniola from Mexico via Cuba. It is highly likely that Plectreuridae will be discovered as an element of the extant Hispaniolan fauna in the future, especially given that they occur at the south-east tip of Cuba ( Alayón 2003).

Figures

FIGURES 1 – 5. Holotype male of Plectreurys pittfieldi Penney, sp. nov. 1, dorsal view; 2, ventral view; 3, first walking leg; 4, pedipalp; 5, pedipalp.