comment on this calibration
Parasitiformes
Lineage (NCBI):
root
» Eukaryota
» Opisthokonta
» Metazoa
» Eumetazoa
» Bilateria
» Coelomata
» Protostomia
» Ecdysozoa
» Panarthropoda
» Arthropoda
» Chelicerata
» Arachnida
» Acari
» Parasitiformes
| node name Parasitiformes Look for this name in NCBI Wikipedia Animal Diversity Web | ||
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recommended citations Wolfe et al. 2016 |
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node minimum age 98.17 Ma This fossil is sourced from amber mines in the Hukawng Valley of Kachin State, northern Myanmar (formerly Burma). The depositional age of Burmese amber was estimated from U-Pb dating of zircons from the volcaniclastic matrix surrounding the amber (Shi et al.,2012). Shi et al. (2012) argue the amber is not older than its associated sediments, as burial and preservation would have to be rapid for survival of organic material, so the amber was probably formed at, but not earlier than the U-Pb date: at 98.79 Ma±0.62 Myr. Therefore, a minimum age for any fossil from Burmese amber deposits is 98.17 Ma. | ||
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node maximum age 514 Ma A soft maximum constraint comes from the oldest chelicerate W. barbarahardyae from the Emu Bay Shale on Kangaroo Island, SouthAustralia, which has been correlated based on trilobite biostratigraphy to the upper part of the P. janeae Zone in mainland South Australia (Jell in Bengtson et al., 1990; Fig. 2 in Jago et al., 2012). As this is equivalent to the Canglangpuan Stage in South China and the late Botoman inSiberia (Gehling et al., 2011, Fig. 9), the Emu Bay Shale can be dated to Cambrian Series 2, Stage 4, providing a maximum age of ~514 Ma. | ||
| primary fossil used to date this node | ||
Poinar A-10-260 | ||
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phylogenetic justification
Morphological characters such as the subcircular body with a marginal groove, free coxae, ventral anal opening, the presence of a capitulum and Haller's organ, absence of an anal groove, and elongate four segmented palpi are all suggestive of Parasitiformes affinity for C. burmanicum (Poinar and Brown, 2003). A particularly diagnostic character, suggesting placement within at least total-group Ixodida (and thus crown Parasitiformes), is the presence of claws on palpal segment 3 in the larva (Poinar and Brown, 2003). Putative morphologies similar to bacterial pathogens exclusive to modern Ixodida were recently described from the paratype (Poinar, 2015). |
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phylogenetic reference(s)
Poinar, G., Brown, A.E. 2003. A new genus of hard ticks in Cretaceous Burmese amber (Acari: Ixodida: Ixodidae). Syst. Parasitol. 54, 199–205.
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| tree image (click image for full size) | ||
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Figure 4 from Wolfe et al. (2016).
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