Romer's gap
Romer's gap | ||
−360 — – −355 — – −350 — – −345 — – −340 — – −335 — – −330 — – −325 — – −320 — – −315 — – −310 — – −305 — – −300 — – −295 — | Palæozoic | |
Known fossil ranges.
Ghost lineages.
1: "
Romer's gap is an example of an apparent gap in the
Age
Romer's gap runs from approximately 360 to 345 million years ago, corresponding to the first 15 million years of the
Mechanism behind the gap
There has been long debate as to why there are so few fossils from this time period.
While initial
Aquatic vertebrates, which include most tetrapods during the Carboniferous,
The low diversity of marine fishes, particularly shell-crushing predators (
Gap fauna
The gap in the tetrapod record has been progressively closed with the discoveries of such early Carboniferous tetrapods as
However, tetrapod material in the earliest stage of the Carboniferous, the
Recent analysis of the Blue Beach deposits in Nova Scotia suggest that "the early tetrapod fauna is not easily divisible into Devonian and Carboniferous faunas, suggesting that some tetrapods passed through the end Devonian extinction event unaffected."[13]
Tournaisian-age locations
For many years after Romer's gap was first recognised, only two sites yielding Tournaisian-age tetrapod fossils were known; one is in East Lothian, Scotland, and another in Blue Beach, Nova Scotia, where in 1841, Sir William Logan, the first Director of the Geological Survey of Canada, found footprints from a tetrapod.[14][note 1][15] Blue Beach maintains a fossil museum that displays hundreds of Tournaisian fossils, which continue to be found as the cliff erodes to reveal new fossils.[16]
In 2012, 350-million-year-old tetrapod remains from four new Tournaisian sites in Scotland were announced, including those from a primitive amphibian nicknamed "Ribbo".[17] In 2016, five more species were unearthed from these localities,[4] proving Scotland to be one of the most important sites in the world for understanding this time period.[18]
These localities are the coast of Burnmouth, the banks of the Whiteadder Water near Chirnside, the River Tweed near Coldstream, and the rocks near Tantallon Castle alongside the Firth of Forth. Fossils of both aquatic and terrestrial tetrapods are known from these localities, providing an important record of the transition between life in water and life on land[19] and filling some of the lacunae in Romer's gap. These new localities may represent a larger fauna, as all lie within a short distance of each other and share many fishes with the nearby and contemporary Foulden fish bed locality (which has not produced tetrapods thus far).[7][19] As with East Kirkton Quarry, tetrapods at these sites were discovered through the long-term efforts of Stan Wood and colleagues.[19]
In April 2013 scientists associated with the British Geological Survey (BGS) and the National Museums of Scotland announced the TW:eed project (Tetrapod World: early evolution and diversification). This project includes collaborators from across the UK, and aims to gather knowledge on the end-Devonian Early-Carboniferous world. One aim has been to drill a continuous 500-meter (1,640 ft) borehole at an undisclosed location near Berwick-upon-Tweed. This has produced a complete, centimetre-scale sampling of Tournaisian sediment, without discontinuities, providing a timeline on which fossil discoveries can be accurately placed.[20] In the most recent paper to be produced by the TW:eed team, they announced some initial results from the core, including the apparent lack of oxygen excursion across Romer's Gap.[4] This suggests that previous theories about low oxygen being the cause of Romer's Gap will need to be re-evaluated.
See also
References
- PMID 22393016.
- ISSN 0181-0642.
- ^ By 1955 (perhaps even earlier), Romer states that few good fossils of tetrapods have been recovered from early Carboniferous deposits. See: Romer, Alfred Sherwood (presented: November 11, 1955 ; published: June 28, 1956) "The early evolution of land vertebrates," Proceedings of the American Philosophical Society, 100 (3) : 151-167; see especially page 166. Available on-line at: JSTOR.
- ^ S2CID 22421017.
- ^ Tarlach, Gemma (December 5, 2016). "Tetrapod Triumph! Solving Mystery Of First Land Vertebrates". dead things. Discover. Archived from the original on August 3, 2019. Retrieved December 22, 2016.
- ^ a b c d e f
PMID 17065318.
- ^ a b c d e f g h i j k l
Sallan, Lauren Cole; Coates, Michael I. (1 June 2010). "End-Devonian extinction and a bottleneck in the early evolution of modern jawed vertebrates". PMID 20479258.
- ^ a b c d e Coates, Michael I.; .
- ^ a b c
Sallan, Lauren Cole; Kammer, Thomas W.; Ausich, William I.; Cook, Lewis A. (17 May 2011). "Persistent predator-prey dynamics revealed by mass extinction". PMID 21536875.
- ^ a b
OCLC 47767251.
- ^
Kammer, Thomas W.; Ausich, William I. (June 2006). "The "Age of Crinoids": A Mississippian biodiversity spike coincident with widespread carbonate ramps" (PDF, 0.6 MB). S2CID 10822498.
- ^ "Paleos Proterozoic: Proterozoic sites". 9 April 2002. Archived from the original on 2009-02-24. Retrieved 2012-03-06.
- PMID 25915639.
- ^ Logan, William Edmond (1842). "On the coal-fields of Pennsylvania and Nova Scotia". Proceedings of the Geological Society of London. 3: 707–712. From p. 712: "At Horton Bluff, ten miles north of Windsor [, Nova Scotia], … he also obtained a slab which appears to him to exhibit foot-marks, … "
- ^ "Blue Beach Fossil Museum". 9 May 2012. Retrieved 2012-05-09.
- ^ "Blue Beach Fossil Museum". 9 May 2012. Retrieved 2012-05-09.
- ^ Chirnside fossils could provide key to Romer’s Gap Already the collection has revealed one notable amphibian specimen that has been nicknamed ‘Ribbo’ due to its prominent and well-preserved ribs, providing scientists with enough information to interpret what the creature may have looked like as it roamed the Tweed basin around 350 million years ago.
- ^ "Scotland holds the key to understanding how life first walked on land". the Guardian. 2016-02-19. Retrieved 2022-11-30.
- ^ PMID 22393016.
- ^ "Fossil hunters dig deep in Scottish Borders", news.Scotsman.com: accessed 6 April 3013
Notes
- ^ During 1841–1842, Scottish geologist Charles Lyell visited North America, including Nova Scotia. In 1843, Lyell mentioned Logan's discovery of footprints in the Carboniferous deposits of Horton Bluff. English paleontologist Richard Owen claimed that Logan's footprints were those of a reptile. See:
- Lyell, Charles (1843). "On the coal formation of Nova Scotia, and on the age and relative position of the gypsum accompanying marine limestones". Proceedings of the Geological Society of London: 184–186. ; see p. 185. From p. 185: "With these Mr. Lyell found in Horton Bluff scales of a ganoid fish, and in the ripple-marked sandstones of the same place, Mr. Logan discovered footsteps, which appeared to Mr. Owen to belong to some unknown species of reptile, constituting the first indications of the reptilian class known in the carboniferous rocks."
- Reprinted in: Lyell, Charles (1843). "On the coal formation of Nova Scotia, and on the age and relative position of the gypsum accompanying marine limestones". American Journal of Science and Arts. 45: 356–358. ; see p. 358.