• Source: Ballagan Formation

The Ballagan Formation is a geologic formation in Scotland and England. It preserves fossils dating back to the early part of the Carboniferous period (Tournaisian – early Visean). Its name comes from the "Ballagan Beds" of Ballagan Glen, near Strathblane, which has a good example of this geological formation.
The Ballagan Formation was historically known as the Cementstone Group, but more recently it has been placed as the middle formation of the Inverclyde Group. This change was motivated by the recognition that the youngest parts of the Devonian Upper Old Red Sandstone (now known as the Kinnesswood Formation) were geologically continuous with the lowest parts of the Lower Carboniferous Calciferous Sandstone Measures (now known as the Ballagan and Clyde Sandstone formations). This interval of Devonian-Carboniferous overlap was named the Inverclyde Group, and the cementstone-rich "drab beds" in the middle of the group were renamed to the Ballagan Formation. In Lothian, the Ballagan and Clyde Sandstone formations are sometimes known as the Tyninghame Formation.




Fossil sites


Many localities of the Ballagan Formation preserve exceptional fossils. The majority of fossiliferous sites are in the Midland Valley (particularly the Scottish Borders and East Lothian), in the southeast corner of Scotland.
One of the earliest sites to be studied was the fish bed at Foulden, which hosts many well-preserved fish fossils, notably including endemic actinopterygians (ray-finned fish) and the first complete skeleton of a rhizodont. Plants and arthropods also form a significant portion of Foulden fossils. This site and its fish fossils were publicized by E.I. White in 1927, and further excavations were performed by Stan Wood in 1980-1981. The Foulden fish bed was the primary theme for volume 76 of the Transactions of the Royal Society of Edinburgh: Earth Sciences journal, published in 1985.
Willie's Hole, near Chirnside, is another site known for its high quality of preservation. It was initially recognized for its crustacean fossils, forming "shrimp beds" akin to those observed throughout the later Scottish Carboniferous. Willie's Hole has continued to produce well-preserved fossils of arthropods, fish, and partial tetrapod skeletons.

By far the largest exposures of the Ballagan Formation occur along the coastal end cliffs of Burnmouth. Tetrapod, fish, and arthropod fragments are common in several layers at Burnmouth, not just in fine-grained overbank deposits but also coarse river channel conglomerates, an unusual mode of preservation.
Tetrapod fossils have been found in the vicinity of Tantallon Castle. Additional Midland Valley sites include Crumble Edge (along Whiteadder Water), Coldstream, Cockburnspath, Cove (in Berwickshire), and Whitrope Burn (near Hawick). A few locales in nearby Northumberland, England encompass fossil-bearing outcrops of the Ballagan Formation, such as Berwick-upon-Tweed Barrow Scar (near Alwinton), and a borehole core at Norham.
Some sites are also found along the west coast of Scotland. Auchenreoch Glen, near Dumbarton, was the collection site for the nearly complete type fossil of Pederpes finneyae, which was the oldest named tetrapod of the Carboniferous upon its discovery. Diverse assemblages of fish teeth and other microfossils have been found at Ayrshire and at Hawk's Nib and Mill Hole, on the Isle of Bute.




Paleobiota


The Ballagan Formation preserves a plethora of tetrapod, fish, and invertebrate fossils, reconstructing one of the most diverse continental ecosystems known from the Tournaisian stage. A variety of plant megafossils and spores are known from the Ballagan Formation.




= Tetrapods

=
Aytonerpeton microps
Diploradus austiumensis
Koilops herma
Mesanerpeton woodi
Ossirarus kierani
Pederpes finneyae (Whatcheeriidae)
Perittodus apsconditus
Tantallognathus woodi
UMZC 2011.7.2: A small unnamed five-fingered tetrapod similar to Gephyrostegus and Silvanerpeton
SPW 4165 ("Ribbo"): A large unnamed tetrapod with robust ribs and limbs
Crassigyrinus-like bone fragments
An Eogyrinus-like tetrapod scute
Indeterminate Tetrapoda and Whatcheeriidae fragments.




= Fish

=
Acanthodii ("spiny sharks"): Acanthodes ovensi (Acanthodidae), Gyracanthus sp. (Gyracanthidae), and rare indeterminate Climatiiformes.
Actinisitia (coelacanths): cf. Rhabdoderma
Actinopterygii (ray-finned fish): Aetheretmon valentiacum (Strepheoschemidae), Cosmoptychius striatus (Cosmoptychiidae), Phanerosteon ovensi (Carbovelidae), Strepheoschema fouldenensis (Strepheoschemidae), Styracopterus fulcratus (Styracopteridae)
Chondrichthyes (cartilaginous fish): Ageleodus pectinatus, Cladodus sp. (Ctenacanthiformes?), Cooleyella sp. (Anachronistidae), Deihim sp. (Protacrodontidae), Deltodus tubineus (Cochliodontidae), Harpagofututor sp. (Chondrenchelyidae), Helodus ?simplex (Helodontiformes), Onychoselache (shark fin spines), Platyxystrodus sps. (Chondrenchelyidae), Protacrodus sp. (Protacrodontidae), Whitropus longicalcus (Cochliodontiformes)
Dipnoans (lungfish): Ballagadus caustrimi, Ballagadus rossi, Coccovedus cellatus, Ctenodus roberti, Ctenodus whitropei, Ctenodus williei, Limanichthys fraseri, Occludus romeri, Uronemus splendens, Xylognathus macrustenus
Megalichthyidae: ?Megalichthys sp.
Rhizodonts: cf. Archichthys portlocki, Strepsodus? anculomanensis, cf. Strepsodus sauroides
Indeterminate Actinopterygii.
Indeterminate Chondrichthyes, including Helodontidae, Psephodontidae, Cochliodontiformes, Protacrodontidae, Holocephali, Xenacanthiformes, Hybodontiformes, ctenacanths, and Menaspiformes.
Indeterminate fragments of lungfish and rhizodonts, some estimated up to 3 meters or 10 feet in length




= Invertebrates

=
Eumalacostracan crustaceans ("shrimps"): Bairdops elegans (Permimecturidae), Belotelson traquairi (Belotelsonidae), Dithyocaris, Pseudogalathea, Pseudotealliocaris etheridgei, Tealliocaris
Millipedes: Woodesmus sheari and at least five other millipede taxa, including members of Archipolypoda, Juliformia, and Euphoberiidae
Xiphosurans (horseshoe crabs): Albalimulus bottoni (Limulidae), Rolfeia fouldenensis (Paleolimulidae)
Scorpions: Gigantoscorpio cf. willsi (Gigantoscorpionidae), Trachyscorpio squarrosus (Eoscorpiidae)
Eurypterids: "Cyrtoctenus" (Hibbertopterus) peachi (Hibbertopteridae)
Polyurida aenigmatica, an enigmatic worm-like animal initially mistaken for a myriapod
"Spirorbiform" microconchids, initially mistaken for Spirorbis polychaete worm tubes
Ostracods
Bivalves: Modiolus latus (Mytilidae), Naiadites, Schizodus
Gastropods
Brachiopods




See also



List of fossiliferous stratigraphic units in Scotland




References



Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 17 December 2021.

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