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Cretaceous Canadian amber spider and the palpimanoidean nature of lagonomegopids

100%
Penney D.
Acta Palaeontologica Polonica
|
2004
|
tom 49
|
nr 4
The first formally described spider from mid−Campanian (76.5–79.5 Ma), Upper Cretaceous amber from Cedar Lake, Manitoba, Canada is named as Grandoculus chemahawinensis new genus and species. It belongs in the fossil family Lagonomegopidae, based on the large eyes situated anterolaterally on the carapace. The proposed systematic position of this family in Palpimanoidea was based on tenuous characters, such as spineless legs and a single metatarsal trichobothrium. The new fossil possesses dense scopulae prolaterally on the metatarsus and tarsus of the first pair of legs, confirming placement of the Lagonomegopidae in Palpimanoidea along with the only other known families to exhibit this character. However, the individual setae differ between the new specimen and the other families, in that they have a pointed, hooked−tip on the metatarsus and a straight, pointed tip on the tarsus, rather than a spatulate tip. Both hooked and spatulate setal types presumably evolved from a “normal−type” seta and may represent two different lineages derived from a common ancestor.
2
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A new deinopoid spider from Cretaceous Lebanese amber

100%
Penney D.
Acta Palaeontologica Polonica
|
2003
|
tom 48
|
nr 4
Palaeomicromenneus lebanensis gen. et sp. nov. (Araneae: Deinopidae) is described from Upper Neocomian–basal Lower Aptian (ca. 125–135 Ma) Cretaceous amber from the Hammana/Mdeyrij outcrop, Lebanon. This is the oldest known, and possibly the first true fossil, deinopid. The lack of ocular modifications in the new fossil genus does not exclude it from having exhibited the same net−casting prey capture behaviour as extant deinopids. Alternatively, this prey−capture behaviour may be highly derived and whether it had evolved by the Early Cretaceous cannot be determined for sure; early deinopids (as diagnosed by pedipalp morphology rather than behaviour) may have been orb−web weavers as is their sister taxon the Uloboridae.
3
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Estimating fossil ant species richness in Eocene Baltic amber

63%
Penney D., Preziosi R. F.
Acta Palaeontologica Polonica
|
2014
|
tom 59
|
nr 4
Fossil insects in amber are often preserved with life-like fidelity and provide a unique insight to forest ecosystems of the geological past. Baltic amber has been studied for more than 300 years but despite the large number of described fossil species (ca. 3500 arthropods) and abundance of fossil material, few attempts have been made to try and quantify statistically how well we understand the palaeodiversity of this remarkable Fossil-Lagerstätte. Indeed, diversity estimation is a relatively immature field in palaeontology. Ants (Hymenoptera: Formicidae) are a common component of the amber palaeobiota, with more than 100 described species representing approximately 5% of all inclusions encountered. Here we apply quantitative statistical species richness estimation techniques to Baltic amber data for the first time. We use species level data from a sample size of 12 769 specimens and conclude that around 29% of the Baltic amber ant fauna has yet to be discovered. The species richness accumulation curve clearly reaches its asymptote at around 9650 specimens, indicating this as the minimum sample size required for a reasonable estimate of species richness for ants alone. Hence, it is hardly surprising that previous studies concerning so-called “representative” samples of the entire palaeobiota, consisting of at most a few thousand inclusions do not agree with each other. Nonetheless, we demonstrate that it is possible to apply quantitative techniques to amber derived data and this should be the preferred approach wherever possible, rather than generating qualitative conclusions of little value for comparative purposes.
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