The Ballagan Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to th ...

and

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the early part of the Carboniferous period (

Tournaisian The Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The Tournaisian age lasted from Ma to Ma. It is preceded by the Famennian (the uppermost stag ...

– early Visean). Its name comes from the "Ballagan Beds" of Ballagan Glen, near

Strathblane Strathblane ( gd, Strath Bhlàthain, ) is a village and parish in the registration county of Stirlingshire, situated in the southwestern part of the Stirling council area, in central Scotland. It lies at the foothills of the Campsie Fells and th ...

, 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 The Inverclyde Group is a Carboniferous lithostratigraphic group (a sequence of rock strata) in southern Scotland and northernmost England. The name is derived from Inverclyde. The rocks of the Inverclyde Group have also previously been referred ...

. This change was motivated by the recognition that the youngest parts of the Devonian Upper Old Red Sandstone (now known as the

Kinnesswood Formation The Kinnesswood Formation is a geological formation in the Central Lowlands of Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a ...

) 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 Lothian (; sco, Lowden, Loudan, -en, -o(u)n; gd, Lodainn ) is a region of the Scottish Lowlands, lying between the southern shore of the Firth of Forth and the Lammermuir Hills and the Moorfoot Hills. The principal settlement is the Sco ...

, the Ballagan Formation is 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 The Scottish Borders ( sco, the Mairches, 'the Marches'; gd, Crìochan na h-Alba) is one of 32 council areas of Scotland. It borders the City of Edinburgh, Dumfries and Galloway, East Lothian, Midlothian, South Lanarkshire, West Lot ...

and

East Lothian East Lothian (; sco, East Lowden; gd, Lodainn an Ear) is one of the 32 council areas of Scotland, as well as a historic county, registration county and lieutenancy area. The county was called Haddingtonshire until 1921. In 1975, the hi ...

), 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 Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...

(ray-finned fish) and the first complete skeleton of a

rhizodont Rhizodontida is an extinct group of predatory tetrapodomorphs known from many areas of the world from the Givetian through to the Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The ...

. 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 Chirnside is a hillside village in Berwickshire, Scotland, west of Berwick-upon-Tweed and east of Duns, Scottish Borders, Duns. Church The parish church at Chirnside dates from the 12th century. It was substantially rebuilt in 1878 and ex ...

, is another site known for its high quality of preservation. It was initially recognized for its

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

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 Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, oft ...

, fish, and partial tetrapod skeletons.'''' The Spouts Burn - geograph-2396335-by-Lairich-Rig

By far the largest exposures of the Ballagan Formation occur along the coastal end cliffs of

Burnmouth Burnmouth is a small fishing village located adjacent to the A1 road on the east coast of Scotland. It is the first village in Scotland on the A1, after crossing the border with England. Burnmouth is located in the Parish of Ayton, in the Sco ...

. Tetrapod, fish, and arthropod fragments are common in several layers at Burnmouth, not just in fine-grained

overbank An overbank is an alluvial geological deposit consisting of sediment that has been deposited on the floodplain of a river or stream by flood waters that have broken through or overtopped the banks. The sediment is carried in suspension, and becaus ...

deposits but also coarse

river channel In physical geography, a channel is a type of landform consisting of the outline of a path of relatively shallow and narrow body of water or of other fluids (e.g., lava), most commonly the confine of a river, river delta or strait. The word is ...

conglomerates, an unusual mode of preservation. Tetrapod fossils have been found in the vicinity of

Tantallon Castle Tantallon Castle is a ruined mid-14th-century fortress, located east of North Berwick, in East Lothian, Scotland. It sits atop a promontory opposite the Bass Rock, looking out onto the Firth of Forth. The last medieval curtain wall castle to b ...

. Additional Midland Valley sites include Crumble Edge (along

Whiteadder Water Whiteadder Water is a river in East Lothian and Berwickshire, Scotland. It also flows for a very short distance through Northumberland before joining the River Tweed. In common with the headwaters of the Biel Water it rises on the low hillside ...

Coldstream Coldstream ( gd, An Sruthan Fuar , sco, Caustrim) is a town and civil parish in the Scottish Borders area of Scotland. A former burgh, Coldstream is the home of the Coldstream Guards, a regiment in the British Army. Description Coldstream l ...

Cockburnspath Cockburnspath ( ; sco, Co’path) is a village in the Scottish Borders area of Scotland. It lies near the North Sea coast between Berwick-upon-Tweed and Edinburgh. It is at the eastern extremity of the Southern Upland Way a long-distance footpa ...

, Cove (in

Berwickshire Berwickshire ( gd, Siorrachd Bhearaig) is a historic county, registration county and lieutenancy area in south-eastern Scotland, on the English border. Berwickshire County Council existed from 1890 until 1975, when the area became part of ...

), and Whitrope Burn (near

Hawick Hawick ( ; sco, Haaick; gd, Hamhaig) is a town in the Scottish Borders council area and historic county of Roxburghshire in the east Southern Uplands of Scotland. It is south-west of Jedburgh and south-south-east of Selkirk. It is one o ...

). A few locales in nearby

Northumberland Northumberland () is a ceremonial counties of England, county in Northern England, one of two counties in England which border with Scotland. Notable landmarks in the county include Alnwick Castle, Bamburgh Castle, Hadrian's Wall and Hexham Ab ...

encompass fossil-bearing outcrops of the Ballagan Formation, such as

Berwick-upon-Tweed Berwick-upon-Tweed (), sometimes known as Berwick-on-Tweed or simply Berwick, is a town and civil parish in Northumberland, England, south of the Anglo-Scottish border, and the northernmost town in England. The 2011 United Kingdom census recor ...

Barrow Scar (near

Alwinton Alwinton (previously named "Allenton" and sometimes still referred to as this) is a village and former parish in Northumberland, England. Alwinton is named after the nearby River Alwin, and means farm on the River Alwin. Alwinton lies at the h ...

), and a borehole core at

Norham Norham ( ) is a village and civil parish in Northumberland, England, It is located south-west of Berwick on the south side of the River Tweed where it is the border with Scotland. History Its ancient name was Ubbanford. Ecgred of Lindisfarne ( ...

. Some sites are also found along the west coast of Scotland. Auchenreoch Glen, near

Dumbarton Dumbarton (; also sco, Dumbairton; ) is a town in West Dunbartonshire, Scotland, on the north bank of the River Clyde where the River Leven flows into the Clyde estuary. In 2006, it had an estimated population of 19,990. Dumbarton was the ca ...

, 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 A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...

have been found at

Ayrshire Ayrshire ( gd, Siorrachd Inbhir Àir, ) is a Counties of Scotland, historic county and registration county in south-west Scotland, located on the shores of the Firth of Clyde. Its principal towns include Ayr, Kilmarnock and Irvine, North Ayrshi ...

and at Hawk's Nib and Mill Hole, on the

Isle of Bute The Isle of Bute ( sco, Buit; gd, Eilean Bhòid or '), known as Bute (), is an island in the Firth of Clyde in Scotland, United Kingdom. It is divided into highland and lowland areas by the Highland Boundary Fault. Formerly a constituent is ...

Paleobiota

The Ballagan Formation preserves a plethora of

tetrapod Tetrapods (; ) are four-limb (anatomy), limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant taxon, extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (p ...

, fish, and

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

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 ''Aytonerpeton'' is an extinct genus of stem- tetrapod from the Ballagan Formation of Scotland. It was one of five new genera of early limbed vertebrates from the Ballagan Formation described by Clack ''et al.'' in 2016. These vertebrates were a ...

'' * '' Diploradus austiumensis'' * '' Koilops herma'' * '' Mesanerpeton woodi'' * ''

Ossirarus kierani ''Ossirarus'' is an extinct genus of four-limbed stem-tetrapod from the Mississippian (mid-Tournaisian) of Scotland. It contains a single species, ''Ossirarus kierani'', based on disarticulated skull and postcranial bones from the Ballagan Form ...

'' * '' Pederpes finneyae'' (

Whatcheeriidae Whatcheeriidae is an extinct family of tetrapods which lived in the Mississippian sub-period, a subdivision of the Carboniferous period. It contains the genera ''Pederpes'', '' Whatcheeria'', and possibly '' Ossinodus''. Fossils of a possible ...

) * '' Perritodus apsconditus'' * '' Tantallognathus woodi'' * UMZC 2011.7.2: A small unnamed five-fingered tetrapod similar to '' Gephyrostegus'' and ''

Silvanerpeton ''Silvanerpeton'' is an extinct genus of early reptiliomorph found in East Kirkton Quarry of West Lothian, Scotland, in a sequence from the Brigantian substage of the Viséan (Lower Carboniferous). The find is important, as the quarry represent ...

'' * SPW 4165 ("Ribbo"): A large unnamed tetrapod with robust ribs and limbs * ''

Crassigyrinus ''Crassigyrinus'' (from la, crassus, 'thick' and el, γυρίνος el, gyrínos, 'tadpole') is an extinct genus of carnivorous stem tetrapod from the Early Carboniferous Limestone Coal Group of Scotland and possibly Greer, West Virginia. Th ...

''-like bone fragments * An '' Eogyrinus''-like tetrapod scute * Indeterminate Tetrapoda and Whatcheeriidae fragments.

Fish

Acanthodii Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, whic ...

("spiny sharks"): '' Acanthodes ovensi'' ( Acanthodidae), '' Gyracanthus'' sp. (

Gyracanthidae Gyracanthidae is an family of extinct fish belonging to the class Acanthodii, known from early Devonian to late Carboniferous. Members are characterized by large, broad-based, paired fin spines with the pectoral fin spines having a distinct long ...

), and rare indeterminate

Climatiiformes The Climatiiformes is an order of extinct fish belonging to the class Acanthodii. Like most other "spiny sharks", the Climatiiformes had sharp spines. These animals were often fairly small in size and lived from the Late Silurian to the Early Car ...

. * Actinisitia (

coelacanths The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east coast ...

): cf. '' Rhabdoderma'' *

Actinopterygii Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or ...

(ray-finned fish): '' Aetheretmon valentiacum'' ( Strepheoschemidae), '' Cosmoptychius striatus'' ( Cosmoptychiidae), '' Phanerosteon ovensi'' ( Carbovelidae), '' Strepheoschema fouldenensis'' (Strepheoschemidae), '' Styracopterus fulcratus'' ( Styracopteridae) *

Chondrichthyes Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissu ...

(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 are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, in ...

(

lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...

): '' Ballagadus caustrimi'', '' Ballagadus rossi'', '' Coccovedus cellatus'', '' Ctenodus roberti'', '' Ctenodus whitropei,'' '' Ctenodus williei,'' '' Limanichthys fraseri'', '' Occludus romeri,'' '' Uronemus splendens,'' '' Xylognathus macrustenus'' *

Megalichthyidae Megalichthyidae is an extinct family (biology), family of tetrapodomorphs which lived from the Middle Devonian, Middle–Late Devonian to the Early Permian. They are known primarily from freshwater deposits, mostly in the Northern Hemisphere (Eur ...

: ?''

Megalichthys ''Megalichthys'' is a genus of prehistoric lobe-finned fish which lived during the Devonian and Carboniferous periods. It is the type genus of the family Megalichthyidae. The type species is ''M. hibberti''. The species ''M. mullisoni,'' named ...

'' sp. *

Rhizodonts Rhizodontida is an extinct group of predatory tetrapodomorphs known from many areas of the world from the Givetian through to the Pennsylvanian - the earliest known species is about 377 million years ago (Mya), the latest around 310 Mya. Rhizodon ...

: cf. ''Archichthys portlocki'', '' Strepsodus? anculomanensis'', cf. '' Strepsodus sauroides'' * Indeterminate

. * Indeterminate

, including Helodontidae, Psephodontidae, Cochliodontiformes, Protacrodontidae,

Holocephali Holocephali ("complete heads"), sometimes given the term Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. Little is known about these primit ...

, Xenacanthiformes,

Hybodontiformes Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like chondrichthyans, which existed from the late Devonian to the Late Cretaceous. They form the group of Elasmobranchii closest to neoselachians, the clade of modern shar ...

, ctenacanths, and Menaspiformes. * Indeterminate fragments of lungfish and rhizodonts, some estimated up to 3 meters or 10 feet in length

Invertebrates

* Eumalacostracan

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gr ...

shrimps Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are referre ...

"): '' Bairdops elegans'' ( Permimecturidae)'','' '' Belotelson traquairi'' ( Belotelsonidae)'','''' Dithyocaris, Pseudogalathea, Pseudotealliocaris etheridgei,''''

Tealliocaris ''Tealliocaris'' is an extinct genus of pygocephalomorphans from the Carboniferous. Species The genus contains eight described species: *''Tealliocaris caudafimbriata'' *''Tealliocaris etheridgei'' *''Tealliocaris formosa'' *''Tealliocaris ...

'' *

Millipedes Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a resu ...

'': Woodesmus sheari'' and at least five other millipede taxa, including members of

Archipolypoda Archipolypoda is an extinct group of millipedes known from fossils in Europe and North America and containing the earliest known land animals. The Archipolypoda was erected by Scudder (1882) but redefined in 2005 with the description of seve ...

Juliformia Juliformia is a taxonomic superorder of millipedes containing three living orders: Julida, Spirobolida, and Spirostreptida, and the extinct group Xyloiuloidea known only from fossils. Morphology The species possess long cylindrical bodies w ...

, and Euphoberiidae * Xiphosurans (

horseshoe crabs Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and the only living members of the order Xiphosura. Despite their name, they are not true crabs or crustaceans: they are chelicerates, most closely related to arach ...

): '' Albalimulus bottoni'' (

Limulidae Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and the only living members of the order Xiphosura. Despite their name, they are not true crabs or crustaceans: they are chelicerates, most closely related to arach ...

), '' Rolfeia fouldenensis'' ( Paleolimulidae) *

Scorpions Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always end ...

: '' Gigantoscorpio'' cf. ''willsi'' ( Gigantoscorpionidae),'''' '' Trachyscorpio squarrosus'' ( Eoscorpiidae) *

Eurypterids Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is l ...

: '' "Cyrtoctenus" (Hibbertopterus) peachi'' (

Hibbertopteridae Hibbertopteridae (the name deriving from the type genus '' Hibbertopterus'', meaning "Hibbert's wing") is a family of eurypterids, an extinct group of aquatic arthropods. They were members of the superfamily Mycteropoidea. Hibbertopterids were la ...

) * '' Polyurida aenigmatica'', an enigmatic worm-like animal initially mistaken for a

myriapod Myriapods () are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial. The fossil record of myriapods reaches back into the late Silurian, a ...

* "Spirorbiform"

microconchids The order Microconchida is a group of small, spirally-coiled, encrusting fossil "worm" tubes from the class Tentaculita found from the Upper Ordovician to the Middle Jurassic (Bathonian) around the world. They have lamellar calcitic shells, u ...

, initially mistaken for ''

Spirorbis ''Spirorbis'' is a genus of very small () polychaete worms, usually with a white coiled shell. Members of the genus live in the lower littoral and sublittoral zones of rocky shores. ''Spirorbis'' worms usually live attached to seaweeds, but some ...

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ...

worm tubes *

Ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

s *

Bivalves Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...

: '' Modiolus latus'' (

Mytilidae Mytilidae are a family of small to large marine and brackish-water bivalve molluscs in the order Mytilida. One of the genera, '' Limnoperna'', even inhabits freshwater environments. The order has only this one family which contains some 52 ge ...

), '' Naiadites,

Schizodus Schizodus is an extinct genus of shallow marine clams. It lived from the Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the begin ...

'' *

Gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. ...

Brachiopods Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, wh ...

References