Dactyloidites Hall, 1866
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https://doi.org/ 10.4202/app.00965.2021 |
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persistent identifier |
https://treatment.plazi.org/id/039C87CA-FFE9-FF99-47A0-F912FB03FA28 |
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treatment provided by |
Felipe |
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scientific name |
Dactyloidites Hall, 1866 |
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Ichnogenus Dactyloidites Hall, 1866
Type ichnospecies: Dactyloidites asteroides ( Fitch, 1850) , New York, USA, Granville Formation , Cambrian .
Remarks.— Dactyloidites is an ichnogenus that deserves further investigations. It was synonymized with Haentzschelinia Vialov, 1964, and with Brooksella Walcott, 1896 ( Fürsich and Bromley 1985; Pickerill et al. 1993; Wilmsen and Niebuhr 2014; Boyd and McIlroy 2016). Brooksella was later re-described as a body fossil by Ciampaglio et al. (2006). Wilmsen and Niebuhr (2014) revisited the type material of Dactyloidites ottoi and discussed the synonymisation of Haentzschelinia and Dactyloidites . They concluded in accordance with Fürsich and Bromley 1985) that there is no valid argument to use Haentzschelinia as separate ichnogenus. However, Haentzschelinia is still retained as separate ichnogenus by some authors and since its defence by Vialov
1989), Haentzschelinia was mainly used for more radial forms (e.g., Belaústegui et al. 2015; Muñoz et al. 2019) and for post-Palaeozoic forms, although a certain time range is not regarded as ichnotaxobase. Recently, Boyd and McIlroy
2016) described a new ichnospecies of Dactyloidites and emended the diagnosis of this ichnogenus.
? Dactyloidites isp.
Fig. 6 View Fig .
Material. — Eight incomplete traces ( MZM Ge 32950– 32957) from the Zoophycos Bed , about 30 more observed in the field, from Velká nad Veličkou , Czech Republic, Eocene. In average, 10– 15 specimens occur on one square metre, usually arranged in groups with individual burrows about 50–100 mm apart .
Description. —Burrow system with numerous cylindrical galleries radiating from a centre creating radial or fan-like structures up to 70 mm in diameter. Individual tunnels have a constant diameter of about 1 mm. They are commonly unbranched and rarely bifurcating at acute angles near their blind tapering endings. The individual J-shaped tunnels usually form multiple layers and are not lined or coated with pellets. The burrows are circular in cross-section and do not overlap. Unlike the specimens that are usually referred to Dactyloidites , the central axis of the observed specimens consists of multiple, steeply inclined to subvertical shafts; the parts of shafts connecting the galleries with the surface were not observed.
Remarks. —Species of at least four different ichnogenera are similar to the studied material: Asterosoma Otto, 1854 , Phycodes Richter, 1850 , Phymatoderma Brongniart, 1849 , and Dactyloidites Hall, 1886 . However, none of the first three fits perfectly. Species of Asterosoma have a concentrically layered wall around a passively filled lumen. Some of our more fan-like specimens resemble Phycodes auduni Dam, 1990 , or Phycodes bromleyi Dam, 1990 . However, the ichnospecies of Phycodes are best restricted to burrows having a (sub-)quadrate cross-section ( Seilacher 2000). Ichnospecies of Phymatoderma are irregularly branched, and pellets frequently occur (e.g., Izumi and Yoshizawa 2016). Multiple shafts are not found in any ichnospecies of Dactyloidites . Nevertheless, the defined ichnotaxobases for Dactyloidites matches the studied material best. The ichnogenus Dactyloidites comprises five valid ichnospecies: Dactyloidites ottoi ( Geinitz, 1849) , Dactyloidites asteroides Fitch, 1850 , and Dactyloidites cabanasi (Meléndez in Cabanás, 1966), exhibit simple, less radiating morphotypes, whereas Dactyloidites peniculus D’Alessandro and Bromley, 1986 , and Dactyloidites jordii Boyd and McIlroy, 2016 , represent more complex radiating burrows with multiple layers of tunnels that sometimes are overlapping.
The studied material of? Dactyloidites isp. from the Velká nad Veličkou shares similarities with more densely radiating ichnospecies. Dactyloidites peniculus D’Alessandro and Bromley, 1986 , occurs as a radial pile or brush-like structure. The studied material is distinguishable from D. peniculus by presence of dichotomous branching tunnels running from the central shaft without lining or pelleted structure. Dactyloidites jordii Boyd and McIlroy, 2016 , has a bilateral symmetry, exhibits multiple orders of branching, and the burrows display an n-shaped cross-section. In contrast, the studied material has radial or bilateral symmetry (in the case of fan-like morphotypes), exhibits only first order branching, and the cross-section of tunnels is circular. Furthermore, it also shares similarities with D. ottoi (Haentzschelinia ottoi sensu Seilacher 2008 ) such as dichotomous branching of tunnels and a fan to radial outline.
Burrows with helicoidal spreiten
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