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''Bairdops'' is an extinct
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
of
mantis shrimp Mantis shrimp, or stomatopods, are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 340 million years ago. Mantis shrimp typically grow to around in length ...
that lived during the
Early Carboniferous Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Early ...
period in what is now Scotland and the United States. Two named species are currently assigned to it. The
type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...
, ''B. elegans'', has been collected from several
Dinantian Dinantian is the name of a series or epoch from the Lower Carboniferous system in Europe. It can stand for a series of rocks in Europe or the time span in which they were deposited. The Dinantian is equal to the lower part of the Mississippian ...
-aged localities in Scotland, and was first described in 1908 by British geologist
Ben Peach Benjamin Neeve Peach (6 September 1842 – 29 January 1926) was a British geologist. Life Peach was born at Gorran Haven in Cornwall on 6 September 1842 to Jemima Mabson and Charles William Peach, an amateur British naturalist and geologi ...
as a species of ''
Perimecturus ''Perimecturus'' is an extinct genus of mantis shrimp that lived during the Early Carboniferous period in what is now Scotland and the United States. The first known specimens were collected near the River Esk, Dumfries and Galloway, River Esk in ...
''. The generic name was coined decades later in 1979 by American paleontologist
Frederick Schram Frederick Robert Schram (born August 11, 1943, in Chicago, Illinois) is an American palaeontologist and carcinologist. He received his B.S. in biology from Loyola University Chicago in 1965, and a Ph.D. on palaeozoology from the University of Ch ...
, and honors William Baird. A later species, ''B. beargulchensis'', was named in 1978 after the
Serpukhovian The Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from Ma to Ma. It is preceded by the Visean and is followed b ...
-aged
Bear Gulch Limestone The Bear Gulch Limestone is a limestone-rich geological lens in central Montana, renowned for the quality of its late Mississippian-aged fossils. It is exposed over a number of outcrops northeast of the Big Snowy Mountains, and is often considere ...
of
Montana Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...
where it was discovered. The two species were originally deemed close relatives based on their physical similarities, but several
cladistic analyses Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...
published since 1998 have suggested the genus may be
polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
. A
carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...
like all mantis shrimps, ''Bairdops'' handled food with its
raptorial The term ''raptorial'' implies much the same as ''predatory'' but most often refers to modifications of an arthropod's foreleg that make it function for the grasping of prey while it is consumed, where the gripping surfaces are formed from the o ...
thoracic appendages and has been proposed to either predominantly be a
scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...
or a
predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
of crustaceans and small fish. Early mantis shrimps like such as this genus would have been unable to capture prey while standing on the seabed like their modern counterparts and instead are believed to have been
benthopelagic The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer o ...
, perhaps grabbing prey from above while swimming just over the bottom. Members of this genus reached a moderate size, with ''B. beargulchensis'' having a
carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the und ...
length of and a total
abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the tors ...
length of , while the slightly smaller ''B. elegans'' reached a carapace length of and a total abdomen length of . Because the various sites from which ''B. elegans'' fossils have been collected represent a wide range of habitats including
marine environments Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea (the term ''marine'' comes from the Latin ''mare'', meaning sea or ocean). A habitat is an ecological or environmental ...
,
brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
bays and even a lake, this species is believed to have been tolerant of a wide
salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
range. Its preferred habitat appears to be marine since most of its specimens originate from such a setting, and it only lived in the aforementioned lake when the water was brackish, disappearing from it after its salinity dropped below the animal's tolerance range. ''B. beargulchensis'' is only known to have inhabited the marine bay where the Bear Gulch Limestone was deposited, a location which was 10 to 12 degrees north of the
equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...
and had a
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal osci ...
climate.


Discovery and naming

The fossilized remains of ''Bairdops'' have been discovered decades prior to the establishment of the genus. In 1908,
Ben Peach Benjamin Neeve Peach (6 September 1842 – 29 January 1926) was a British geologist. Life Peach was born at Gorran Haven in Cornwall on 6 September 1842 to Jemima Mabson and Charles William Peach, an amateur British naturalist and geologi ...
became the first to study specimens of this animal, which were collected in Scotland by A. Macconochie. However, Peach believed they represented members of ''
Perimecturus ''Perimecturus'' is an extinct genus of mantis shrimp that lived during the Early Carboniferous period in what is now Scotland and the United States. The first known specimens were collected near the River Esk, Dumfries and Galloway, River Esk in ...
'', another genus of early
stomatopod Mantis shrimp, or stomatopods, are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 340 million years ago. Mantis shrimp typically grow to around in length ...
s. He erected the species ''Perimecturus elegans'' based on remains found near the River Esk in
Glencartholm Glencartholm is a location in Dumfries and Galloway, southern Scotland, along the River Esk. The Glencartholm Volcanic Beds contain a Palaeozoic (specifically Carboniferous) fossil fish site of international importance. Discovered in 1879, mo ...
. In addition, he also erected the species ''Perimecturus ensifer'' from fossils found in
Liddel Water Liddel Water is a river running through southern Scotland and northern England, for much of its course forming the border between the two countries, and was formerly one of the boundaries of the Debatable Lands. Liddel Water's source is beneat ...
,
Newcastleton Newcastleton, also called Copshaw Holm, is a village in Liddesdale, the Scottish Borders, a few miles from the border with England, on the Liddel Water. It is within the county of Roxburghshire. It is the site of Hermitage Castle. Newcastleton ...
and Glencartholm. In 1979,
Frederick Schram Frederick Robert Schram (born August 11, 1943, in Chicago, Illinois) is an American palaeontologist and carcinologist. He received his B.S. in biology from Loyola University Chicago in 1965, and a Ph.D. on palaeozoology from the University of Ch ...
found that ''P. elegans'' and ''P. ensifer'' were indistinguishable from each other, thus the latter was declared as a junior synonym of the former. He also noted that the tail fan, body shape and size of this species differed significantly from what is seen in other species of ''Perimecturus''. Schram therefore erected the genus ''Bairdops'' with ''P. elegans'' as the
type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...
, which was subsequently renamed as ''Bairdops elegans'', and the specimen GSE 5879 was designated as the
lectotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...
of this species. The generic name honors William Baird, the Assistant Curator of the fossil invertebrate collection at the
Royal Scottish museum The National Museum of Scotland in Edinburgh, Scotland, was formed in 2006 with the merger of the new Museum of Scotland, with collections relating to Scottish antiquities, culture and history, and the adjacent Royal Scottish Museum (opened in ...
. Additionally, Schram described a second species of ''Bairdops'' in 1978 which he named ''B. beargulchensis''. The
specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...
refers to the
Bear Gulch Limestone The Bear Gulch Limestone is a limestone-rich geological lens in central Montana, renowned for the quality of its late Mississippian-aged fossils. It is exposed over a number of outcrops northeast of the Big Snowy Mountains, and is often considere ...
in
Fergus County, Montana Fergus County is a county in the U.S. state of Montana. As of the 2020 census, the population was 11,446. Its county seat is Lewistown. The county was founded in 1885 and named for James Fergus, a Montana politician who was instrumental in cre ...
, where the
holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...
(UM 6217) was collected. Factor and Feldman (1985) declared this species to be a junior synonym of '' Tyrannophontes theridion''. However, a later study by Jenner ''et al.'' (1997) found that ''B. beargulchensis'' is most similar to ''B. elegans'', thus revalidating ''B. beargulchensis''. They also found that some of the fossils in Schram's original sample represent a separate species they named ''Tyrannophontes acanthocercus'' (now moved to the genus '' Daidal''), and that this is likely responsible for the earlier study finding ''B. beargulchensis'' similar to ''Tyrannophontes''.


Description

''Bairdops'' is a crustacean of moderate size, with ''B. elegans'' having a
carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the und ...
length of and a total
abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the tors ...
length of . ''B. beargulchensis'' is slightly larger and more robust, with a carapace ranging from and a total abdomen length of . The
rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...
is about a third the length of the carapace and is spatula-like in shape, with a tapering, pointed tip and a wide base. The antennae are not well preserved, but it is known the scaphocerite (
exopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plu ...
of the antenna) is very large. A pair of large and circular compound eyes are present on the head. The large, elongated carapace covers the entire
thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the ...
in ''B. elegans'', whereas in ''B. beargulchensis'' it leaves only the top of the eighth thorax segment exposed. The carapace has a subrectangular shape and a furrow on its edges. This furrow is prominent in ''B. elegans'' but very slight in ''B. beargulchensis''. The back margin of the carapace is concave at the top, with its sides extending slightly further and reaching the front of the first abdominal segment. Pairs of
raptorial The term ''raptorial'' implies much the same as ''predatory'' but most often refers to modifications of an arthropod's foreleg that make it function for the grasping of prey while it is consumed, where the gripping surfaces are formed from the o ...
appendages are attached to the thorax, though it is unclear whether there are four or five pairs of these. The coxae, ischiomeri and
carpi Carpi may refer to: Places * Carpi, Emilia-Romagna, a large town in the province of Modena, central Italy * Carpi (Africa), a city and former diocese of Roman Africa, now a Latin Catholic titular bishopric People * Carpi (people), an ancien ...
of these appendages are short, whereas the propodi (penultimate segment) and dactyli (final segment) are longer. The longest segment of a raptorial appendage in ''Bairdops'' is the
basis Basis may refer to: Finance and accounting *Adjusted basis, the net cost of an asset after adjusting for various tax-related items *Basis point, 0.01%, often used in the context of interest rates * Basis trading, a trading strategy consisting o ...
. Though Schram and Horner (1978) claimed the propodi of ''B. beargulchensis'' possessed two rows of spines, this observation was based on specimens now reassigned to '' Daidal acanthocercus''. Propodus spines are currently believed to only be present in ''B. elegans''. All thoracic segments are shorter than the abdominal segments. The thoracic segments further front possess narrow
sternite The sternum (pl. "sterna") is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the ...
s and are smaller than the sixth to eighth thoracic segments. The abdominal segments decrease in both height and width down the animal's length, and their side margins are rather straight. Moderate furrows are present on the lower margins of each abdominal segment. In ''B. beargulchensis'', the fifth and sixth abdominal segments may possess one or two backward-pointing ridges extending past the back margin of their respective segments, a feature absent in ''B. elegans''. The somewhat delicate tail fan includes a
telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...
which tapers into a long median spine, while a shorter spine is present on either side of this median spine. Three keels are seen on the telson, with one running down the middle and another on either side of it, which all converge near the end of the telson. The protopod (basal segment) of the
uropod Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion. Definition Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...
has a projection extending over the
ramus Ramus can refer to: * A branch (botany) * A portion of a bone (from Latin ''ramus'', "branch"), as in the Ramus of the mandible or Superior pubic ramus * A nerve ramus such as the Dorsal ramus of spinal nerve * A taxonomic rank ("branch" in English ...
, while the blade-like exopod is made up of a
sclerotised Sclerotin is a component of the cuticle of various Arthropoda, most familiarly insects. It is formed by cross-linking members of particular classes of protein molecules, a biochemical process called sclerotization, a form of tanning in which qu ...
outer part and more membranous inner part.


Classification

Fossil specimens of ''Bairdops'' were first assigned to the family Perimecturidae by Ben Peach in 1908, and to this day the genus is still placed within this family. Peach believed Perimecturidae to be intermediate forms between
Lophogastridae Lophogastridae is a family of crustaceans belonging to the order Lophogastrida. Genera: * ''Ceratolepis'' G.O.Sars, 1883 * '' Chalaraspidum'' Willemoes-Suhm, 1895 * ''Gnathophausia ''Gnathophausia'' is a genus of lophogastrid crustacean. Th ...
and
Anaspididae Anaspididae is a family of freshwater crustacean that is endemic to Tasmania, Australia. The family contains 3 genera and 5 species. This group of crustaceans are considered living fossils. They are commonly and collectively known as the Tasmani ...
, and assigned the family to the currently defunct order
Schizopoda Schizopoda is a former taxonomical classification of a division of the class Malacostraca. Although it was split in 1883 by Johan Erik Vesti Boas into the two distinct orders Mysidacea The Mysidacea is a group of shrimp-like crustaceans in th ...
. It was not until 1962 that the Perimecturidae family were recognized to be early forms of mantis shrimps, when H. K. Brooks reassigned the family to the
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
Palaeostomatopoda (currently delisted as a
suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
and named Palaeostomatopodea). As cladistic analysis became more widely conducted, the palaeostomatopods were first recovered to be a
paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
grouping by Jenner ''et al.'' (1998), and this paraphyly was then confirmed by Schram (2007). The paraphyletic use of Palaeostomatopodea is used today for the convenience of referring to the
evolutionary grade A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Definition An evolutionary grade is a group of s ...
. Though ''B. elegans'' and ''B. beargulchensis'' were initially placed in the same genus due to their overall similarity, the
monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...
of the genus has been questioned. Jenner ''et al.'' (1998) was the first to propose that ''Bairdops'' may be
polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
, recovering ''B. beargulchensis'' to be closer to ''
Perimecturus ''Perimecturus'' is an extinct genus of mantis shrimp that lived during the Early Carboniferous period in what is now Scotland and the United States. The first known specimens were collected near the River Esk, Dumfries and Galloway, River Esk in ...
'' than ''B. elegans''. Schram (2007) similarly suggested ''Bairdops'' to be polyphyletic, but instead found that ''B. elegans'' was the
sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...
to ''Perimecturus rapax''. Haug ''et al.'' (2010) recovered ''B elegans'' as the second-earliest lineage of mantis shrimps to diverge (with ''Archaeocaris'' being the most
basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...
), being a sister taxon to the clade including all other mantis shrimps except ''Archaeocaris''. Smith ''et al.'' (2023) conducted a
phylogenetic analysis In biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that pro ...
which also supports the idea that ''Bairdops'' is polyphyletic, though the family Perimecturidae was found to be monophyletic. Their results are displayed in the
cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
below:


Palaeobiology


Feeding

Like all other mantis shrimp species, ''Bairdops'' would have been
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...
, using its raptorial thoracic appendages to handle prey. Clarkson (1985) suggested that small fish and the crustacean ''
Belotelson ''Belotelson'' is a genus of crustaceans, in the extinct order Belotelsonidea, containing at least two species. It was first named by Packard in 1886 from material found in the Mazon Creek ''lagerstätte'' in Illinois. Its fossils have been found ...
'' were among the prey of ''B. elegans''. Unlike modern mantis shrimps of the suborder
Unipeltata Mantis shrimp, or stomatopods, are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 340 million years ago. Mantis shrimp typically grow to around in length, ...
, the raptorial appendages of palaeostomatopods like ''Bairdops'' lack a click-joint mechanism formed by a specialized joint and its associated muscles. Such a mechanism is what allows modern mantis shrimps to quickly extend the second pair of thoracic appendages to capture prey. Lacking this, the appendages of ''Bairdops'' are more similar to the smaller, third to fifth pairs of thoracic appendages in unipeltatans used to manipulate prey after capture. Jenner ''et al.'' (1998) thus proposed that ''Bairdops'' was an opportunistic
scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...
and specialized in dead food. In contrast, Haug and Haug (2021) suggested that since their appendage morphology would not allow them to capture prey from the seabed, early mantis shrimps would instead have been
benthopelagic The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer o ...
predators, possibly capturing prey from above while swimming just above the bottom. This is unlike modern mantis shrimp, which are
bottom-dwelling The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning ...
predators as adults, though their
larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. Th ...
e are benthopelagic and thus studying them could allow better knowledge of early stomatopods.


Salinity tolerance

Fossils of ''Bairdops elegans'' have been collected from various localities in Scotland representing a wide range of
salinities Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ...
. The species is most abundantly found at Glencartholm, which was a marginal to fully
marine environment Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea (the term ''marine'' comes from the Latin ''mare'', meaning sea or ocean). A habitat is an ecological or environmen ...
at the time of deposition, but some specimens are also found at sites representing
brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
bays (
Newcastleton Newcastleton, also called Copshaw Holm, is a village in Liddesdale, the Scottish Borders, a few miles from the border with England, on the Liddel Water. It is within the county of Roxburghshire. It is the site of Hermitage Castle. Newcastleton ...
and the
Granton Shrimp Bed The Granton Shrimp Bed is a fossil-bearing deposit exposed on the southern shore of the Firth of Forth near Edinburgh, in Scotland. It is classified as a Konservat-Lagerstätten because of the exceptional quality of preservation of the fossils and ...
). Several remains have even been found at the Foulden Fish Bed, representing an occurrence of the species in a non-marine lake. The range of environments in which ''B. elegans'' occurs suggests this species had broad salinity tolerance, though it was most common in marine habitats.


Palaeoenvironment

The geologically oldest known record of ''Bairdops'' is represented by remains of ''B. elegans'' from the lower part of the Foulden Fish Bed, a site within the
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, ne ...
in Scotland. This locality dates to the
Dinantian Dinantian is the name of a series or epoch from the Lower Carboniferous system in Europe. It can stand for a series of rocks in Europe or the time span in which they were deposited. The Dinantian is equal to the lower part of the Mississippian ...
series, and the lack of definitively marine species in its fossil content suggests the Foulden Fish Bed was a non-marine lake at the time of deposition. This lake would have been near the sea and was susceptible to fluctuations in salinity and water level. As a result, the horizons of the Fish Bed show a reciprocal relationship in the abundance of
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 ...
s and palaeoniscid fish: the lowest horizon has ''Bairdops elegans'' and numerous ''
Belotelson ''Belotelson'' is a genus of crustaceans, in the extinct order Belotelsonidea, containing at least two species. It was first named by Packard in 1886 from material found in the Mazon Creek ''lagerstätte'' in Illinois. Its fossils have been found ...
'' fossils, which abruptly become absent in the horizon directly above while palaeoniscids appear (likely arriving from another lake at a time of higher water levels) and persist to the top of the Bed. In an upper horizon, ''Belotelson'' reappears in lower numbers than before. However, ''Bairdops elegans'' appears to have only lived in this lake during the deposition of the lowest horizon, when the lake was brackish and had few fish. It was likely
extirpated Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...
from this area when the water level rose, lowering the salinity beyond its range of tolerance and allowing fish which preyed on it to invade, and failed to recolonize the lake the way ''Belotelson'' did. Fossils of ''Bairdops elegans'' are also known from other Dinantian-aged deposits in Scotland. Two localities in which the species occurs, the
Granton Shrimp Bed The Granton Shrimp Bed is a fossil-bearing deposit exposed on the southern shore of the Firth of Forth near Edinburgh, in Scotland. It is classified as a Konservat-Lagerstätten because of the exceptional quality of preservation of the fossils and ...
and Newcastleton, represent brackish interdistributary bays. The Granton Shrimp Bed has one of the most diverse Dinantian fossil assemblages of crustaceans in Britain, and has been interpreted to represent periodically exposed mudflats at a low water stand of a lagoon. The sediment was anoxic just under the surface. The most abundant crustacean at the Granton Shrimp Bed is ''
Waterstonella ''Waterstonella grantonensis'' is a species of fossil crustacean so distinct from other crustaceans that it has been placed in its own genus, ''Waterstonella'', family, Waterstonellidae, and order, Waterstonellidea. It is named after Charles ...
'', a small swimming species which has been proposed to be a prey item for ''Bairdops''. Other crustaceans from the site include ''
Crangopsis ''Crangopsis'' is an extinct genus of crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepo ...
'', '' Minicaris'', '' Palaemysis'', ''
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 ...
'', '' Pseudogalathea'', '' Anthracocaris'' and ''
Eocypridina ''Eocypridina'' is an extinct genus of ostracods which lived from the Devonian to early Triassic periods in the United States and Scotland. It was first named in 1960, with ''E. campbelli'' as its type species. Discovery and naming Fossils of '' ...
''. Different animal groups such as fish (including ''
Rhadinichthys ''Rhadinichthys'' is an extinct genus of prehistoric bony fish. It is known from several species that lived in the Late Devonian epoch, the Carboniferous period and the Cisuralian epoch (early Permian) in what is now Europe, South Africa, and ...
'' and 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 ...
),
hydrozoa Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specializ ...
ns and molluscs are also represented. The site where the most specimens of ''B. elegans'' have been found is the
Glencartholm Glencartholm is a location in Dumfries and Galloway, southern Scotland, along the River Esk. The Glencartholm Volcanic Beds contain a Palaeozoic (specifically Carboniferous) fossil fish site of international importance. Discovered in 1879, mo ...
Volcanic Beds, deposited in a nearshore marine environment. This locality has the most marine influence of all sites which have yielded ''B. elegans'' remains, and its abundance here may suggests this is the preferred habitat for the species. ''Bairdops'' is deemed a common crustacean in this area, as are ''Belotelson'', ''Anthracocaris'', ''
Perimecturus ''Perimecturus'' is an extinct genus of mantis shrimp that lived during the Early Carboniferous period in what is now Scotland and the United States. The first known specimens were collected near the River Esk, Dumfries and Galloway, River Esk in ...
'' and '' Anthracophausia'', while ''Crangopsis'', ''
Pseudotealliocaris ''Tealliocaris'' is an extinct genus of pygocephalomorphans from the Carboniferous. Species The genus contains eight described species: *''Tealliocaris caudafimbriata'' *''Tealliocaris etheridgei'' *''Tealliocaris formosa'' *''Tealliocaris ...
'' and '' Sairocaris'' are even more abundant than the aforementioned taxa. Fish are also well-represented within the Beds, with more than 200 specimens of over 30 species known. Fossils of plants,
bivalve 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 ...
s,
scorpion 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 endi ...
s and
xiphosura Xiphosura () is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs (a name applied more specifically to the only extant family, Limulidae). They first appeared in the Hirnantian (Late Ordovician). Current ...
ns have also been found in the area. The species ''Bairdops beargulchensis'' is known only from the
Bear Gulch Limestone The Bear Gulch Limestone is a limestone-rich geological lens in central Montana, renowned for the quality of its late Mississippian-aged fossils. It is exposed over a number of outcrops northeast of the Big Snowy Mountains, and is often considere ...
of Montana, which dates to the
Serpukhovian The Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from Ma to Ma. It is preceded by the Visean and is followed b ...
stage of the early Carboniferous period, approximately 324 million years ago. Thus, ''B. beargulchensis'' is geologically younger than any known occurrence of ''B. elegans''. During this time, central Montana was located 10 to 12 degrees north of the
equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...
, at the boundary between an arid belt in the north and a tropical belt in the south. The area would have had a
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal osci ...
al climate with distinct wet summer and dry winter seasons, comparable to the climate of the modern African
Sahel The Sahel (; ar, ساحل ' , "coast, shore") is a region in North Africa. It is defined as the ecoclimatic and biogeographic realm of transition between the Sahara to the north and the Sudanian savanna to the south. Having a hot semi-arid c ...
. The Bear Gulch Limestone is interpreted to have been a marine bay oriented from northwest to southeast. An extremely diverse fossil assemblage is known from this site, with numerous types of fish including chondrichthyans (such as petalodonts,
holocephalans 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 primitiv ...
, symmoriiforms, squatinactids and ''
Thrinacodus ''Thrinacodus'' is an extinct genus of basal elasmobranch, found worldwide from the Late Devonian-Lower Carboniferous. Most species are only known from their tricuspid teeth. ''T. gracia'', originally placed in the separate genus ''Thrinacoselach ...
''),
acanthodians 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, which ...
,
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 ...
and
coelacanth 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 c ...
s. Invertebrates are also found here, including crustaceans,
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 ...
,
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 ...
worms and
cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, ...
s.


References


External links

{{Taxonbar, from=Q124584757 Carboniferous animals of North America Carboniferous invertebrates of Europe Stomatopoda Fossil taxa described in 1979 Prehistoric crustacean genera Prehistoric mantis shrimps