03-11-2020, 08:39 PM
Notes
Unfortunately I will not be unable to provide ‘scientific’ names for as high a proportion of the endemic Trilobite species & larger groups than I have been doing for the region’s endemic Mammals and Birds. My knowledge of this particular group and of “Taxonomists’ Latin” simply isn’t good enough to interpret much of the specialised terminology used in naming the class’s RL members and to recombine this appropriately.
_______________________________________________________
Remember that the Trilobites which survived in the IDU’s home reality have apparently had around 250 million years longer in which to evolve than any of the group’s lineages managed in RL where their recorded existence lasted for “only” around 270 million years (although it must really have been a bit longer than that, with the earlier fossils not yet found…). This allows for some increased diversity in form & lifestyle here, although the roles of swimming predator or planktonic filter-feeder have almost certainly been lost permanently toother types of animal such as ‘Fish’ of various kinds. There are still basic limits, however, on factors such as maximum size or land-dwelling capabilities.
_______________________________________________________
Evidence from RL fossils demonstrates that some types of Trilobite were able to curl up into balls, to protect their less-armoured legs & undersides from attack. It therefore seems likely that some of the species living in our region today can also do so, but this would not be the case for all of them: Lifestyle, threat levels, thickness of armour, and number of body-segments, would presumably be factors to consider.
It is presumed that Trilobites generally had planktonic larvae, but the possibility that females of some types retained their eggs & perhaps also larvae in ‘brood pouches’ inside the front part of their carapace has also been suggested: This would probably be most likely for species living in the most “difficult” environments.
(post 6)
Order: Proetida
Reference: https://en.wikipedia.org/wiki/Proetida
The adult forms of these animals live on the sea-bed, almost entirely below the levels to which light penetrates from the surface, so would have little use for eyesight (unless luminous organisms are extremely common down there…). However, if their larvae are planktonic then those would still find functional eyes useful and so it is possible that the adults of some species do retain functional eyes, although probably not very large or complex ones. (However, again, these are probably the most likely group of Trilobites to retain their eggs in ‘brood pouches’ instead of having planktonic larvae…) These are All species probably possess good senses of smell, for finding food, and some might have evolved a way to track the movements of reasonably-sized creatures nearby through the pressure waves that these cause in the water.
The ancestral forms that lived through the end-Permian mass extinction event here might have been adapted to cope with relatively low oxygen levels, but the extent to which this trait has been retained by modern types is likely to vary.
Suggested possible types
Type One
The adults of this type walk across the sea-bed, mainly scavenging organic scraps for their food but possibly also taking occasional live prey (e.g. worms, sea cucumbers, & other relatively small seabed-feeding organisms, or injured fish that fall into their reach…) as well. Their largest members could reasonably reach lengths of 12-20 inches [25-50cm], as the largest Trilobite fossils found in RL so far were around 16 inches [40cm] and the largest examples found of their current RL ecological counterparts — a marine genus of ‘Isopod’ Crustacean (Bathynomus), related to the terrestrial Woodlice (‘Sow Bugs’, ‘Pill Bugs’) — have been almost 20 inches in length. Slightly larger forms might be possible, in areas where food is relatively abundant (due to, for example, sunken Whale carcasses…), but any oceanographers’ claims to have sighted ones over three feet or so in length should definitely remain unsubstantiated by IC evidence for now: Their plausibility would decrease with increasing size, due not only to food supply limitations but also to biomechanical constraints and to the shortage of suitable cover for shelter from attack while moulting. Waters at those levels are normally quite well-oxygenated by now, so any ancestral adaption for low oxygen levels has quite possibly been lost. If we use those Isopods for comparison then the largest types would probably live in the ‘bathyal zone’ down to maximum depths of around 1.25 miles (2 kilometres), but there could be related species of about half those lengths on the ‘continental slope’ — and perhaps even parts of the continental shelf — above them. Obviously those living regularly closer to the surface would be the likeliest to have retained reasonably good eyesight.
The limits on their rages are probably more-or-less comparable to those for the RL ‘Giant Isopods’. The shallowest waters in which any of these have been found so far were only around 200 feet [22 metres] deep, but that was exceptional and depths of at least 560 feet [170 metres] seem to be more typical. The deepest level at which any of them have been found was around 8’200 feet [2.5 km] down, although the same species involved in that has also been found as close as 1’000 feet [300 metres] to the surface, but 7’000 feet [2.14km] seem to be a more typical limit and most examples of the best-known species are found — possibly due to food supply — at depths of “only” around 1200-2400 feet [365-730 metres].
As the difference in sizes between these and “typical” trilobites is much less than the equivalent difference among the Isopods the label “Giant” is probably used only for the very largest members of this group.
(We could have ‘Giant Deepsea Isopods’ like those RL ones here as well, if people want, but probably in different areas to these trilobites: Maybe, basically, one Ocean for each group?)
Type Two
The adults of these would be significantly smaller than those of Type One, and would be better-adapted for active swimming. They would prey mainly on ‘Sea Cucumbers’ (Echinoderm’ animals, thus related to Starfish & Sea Urchins), which are often relatively abundant at those levels and are ‘deposit feeders’ that extract micro-organisms & organic debris from ingested seabed material: The swimming ability is for moving longer distances to seek their specific prey, instead of just wandering around in the hope that enough food turns up as the larger type presumably does most of the time.
(Potential food supplies at that level are probably too low to support viable populations of Trilobites that deposit-feed directly…)
Type Three
The adults of these would live around the seabed’s ‘hydrothermal vents’ in tectonic ‘rifts’, where the geothermally-heated water can reach very high temperatures. Like the other animals living in those environments they would rely directly or indirectly for food on the chemosynthetic Bacteria which thrive in the mineral-rich waters that rise from within the Earth’s crust there, but their larvae would possibly still be planktonic. Forms adapted for living around vents rather than just seeps would obviously have to have evolved greater tolerance for high temperatures, and probably have some kind of temperature-checking sense (such as eyes adapted to see in infra-red?) as well. Those environments seem to support few significant predators in RL, so the local Trilobites’ armour might have become reduced in thickness and/or in mineralisation. Adaption for relatively low oxygen levels would probably be useful here, as might a greater tolerance for hydrogen sulphide.
Subtype ‘Three A’ simply scrapes bacteria from surfaces, and might have some of its legs adapted for this purpose.
Subtype ‘Three B’ has some of its legs adapted to form a ‘net’ or ‘sieve’ that filters floating bacteria out of the water, if[/]i the currents around the vents & seeps actually allow adequate concentrations of that food-supply [i](which I need to check before confirming that this variety is actually possible…).
Subtype ‘Three C’ actually carries some of the Bacteria as symbiotes, living in pouches of some kind in its own structure, however the RL fossil Trilobites that are thought to have had symbiotic bacteria managed this (which one source says was in specialised structures attached to their gills). It might also consume some bacteria scraped from surfaces, to supplement the symbiotes’ efforts.
Subtype ‘Three D’ takes a more indirect route to that foodstuff: It is an external parasite on the ‘Giant Tube Worms’ (‘Vestimentifera’) that also live at some such sites and that themselves rely on symbiotic bacteria for their nourishment. The adults of this variety would probably be smaller than those of any of the other subtypes listed here.
Type Four, subtypes ‘Four A’ to ‘Four D’: These are similar to Type Three, but live around the cooler ‘methane seeps’ instead and therefore haven’t evolved as great a tolerance for heat: Some of them might also colonise whale carcasses, probably arriving there after major scavengers such as the members of Type One have finished. (Type Three is probably descended from earlier members of Type Four.)
_______________________________________________________
More References
https://en.wikipedia.org/wiki/Giant_isopod
https://en.wikipedia.org/wiki/Whale_fall
https://en.wikipedia.org/wiki/Sea_cucumber
https://en.wikipedia.org/wiki/Hydrothermal_vent
https://en.wikipedia.org/wiki/Cold_seep
(Vestimentifera =) https://en.wikipedia.org/wiki/Siboglinidae
Unfortunately I will not be unable to provide ‘scientific’ names for as high a proportion of the endemic Trilobite species & larger groups than I have been doing for the region’s endemic Mammals and Birds. My knowledge of this particular group and of “Taxonomists’ Latin” simply isn’t good enough to interpret much of the specialised terminology used in naming the class’s RL members and to recombine this appropriately.
_______________________________________________________
Remember that the Trilobites which survived in the IDU’s home reality have apparently had around 250 million years longer in which to evolve than any of the group’s lineages managed in RL where their recorded existence lasted for “only” around 270 million years (although it must really have been a bit longer than that, with the earlier fossils not yet found…). This allows for some increased diversity in form & lifestyle here, although the roles of swimming predator or planktonic filter-feeder have almost certainly been lost permanently toother types of animal such as ‘Fish’ of various kinds. There are still basic limits, however, on factors such as maximum size or land-dwelling capabilities.
_______________________________________________________
Evidence from RL fossils demonstrates that some types of Trilobite were able to curl up into balls, to protect their less-armoured legs & undersides from attack. It therefore seems likely that some of the species living in our region today can also do so, but this would not be the case for all of them: Lifestyle, threat levels, thickness of armour, and number of body-segments, would presumably be factors to consider.
It is presumed that Trilobites generally had planktonic larvae, but the possibility that females of some types retained their eggs & perhaps also larvae in ‘brood pouches’ inside the front part of their carapace has also been suggested: This would probably be most likely for species living in the most “difficult” environments.
(post 6)
Order: Proetida
Reference: https://en.wikipedia.org/wiki/Proetida
The adult forms of these animals live on the sea-bed, almost entirely below the levels to which light penetrates from the surface, so would have little use for eyesight (unless luminous organisms are extremely common down there…). However, if their larvae are planktonic then those would still find functional eyes useful and so it is possible that the adults of some species do retain functional eyes, although probably not very large or complex ones. (However, again, these are probably the most likely group of Trilobites to retain their eggs in ‘brood pouches’ instead of having planktonic larvae…) These are All species probably possess good senses of smell, for finding food, and some might have evolved a way to track the movements of reasonably-sized creatures nearby through the pressure waves that these cause in the water.
The ancestral forms that lived through the end-Permian mass extinction event here might have been adapted to cope with relatively low oxygen levels, but the extent to which this trait has been retained by modern types is likely to vary.
Suggested possible types
Type One
The adults of this type walk across the sea-bed, mainly scavenging organic scraps for their food but possibly also taking occasional live prey (e.g. worms, sea cucumbers, & other relatively small seabed-feeding organisms, or injured fish that fall into their reach…) as well. Their largest members could reasonably reach lengths of 12-20 inches [25-50cm], as the largest Trilobite fossils found in RL so far were around 16 inches [40cm] and the largest examples found of their current RL ecological counterparts — a marine genus of ‘Isopod’ Crustacean (Bathynomus), related to the terrestrial Woodlice (‘Sow Bugs’, ‘Pill Bugs’) — have been almost 20 inches in length. Slightly larger forms might be possible, in areas where food is relatively abundant (due to, for example, sunken Whale carcasses…), but any oceanographers’ claims to have sighted ones over three feet or so in length should definitely remain unsubstantiated by IC evidence for now: Their plausibility would decrease with increasing size, due not only to food supply limitations but also to biomechanical constraints and to the shortage of suitable cover for shelter from attack while moulting. Waters at those levels are normally quite well-oxygenated by now, so any ancestral adaption for low oxygen levels has quite possibly been lost. If we use those Isopods for comparison then the largest types would probably live in the ‘bathyal zone’ down to maximum depths of around 1.25 miles (2 kilometres), but there could be related species of about half those lengths on the ‘continental slope’ — and perhaps even parts of the continental shelf — above them. Obviously those living regularly closer to the surface would be the likeliest to have retained reasonably good eyesight.
The limits on their rages are probably more-or-less comparable to those for the RL ‘Giant Isopods’. The shallowest waters in which any of these have been found so far were only around 200 feet [22 metres] deep, but that was exceptional and depths of at least 560 feet [170 metres] seem to be more typical. The deepest level at which any of them have been found was around 8’200 feet [2.5 km] down, although the same species involved in that has also been found as close as 1’000 feet [300 metres] to the surface, but 7’000 feet [2.14km] seem to be a more typical limit and most examples of the best-known species are found — possibly due to food supply — at depths of “only” around 1200-2400 feet [365-730 metres].
As the difference in sizes between these and “typical” trilobites is much less than the equivalent difference among the Isopods the label “Giant” is probably used only for the very largest members of this group.
(We could have ‘Giant Deepsea Isopods’ like those RL ones here as well, if people want, but probably in different areas to these trilobites: Maybe, basically, one Ocean for each group?)
Type Two
The adults of these would be significantly smaller than those of Type One, and would be better-adapted for active swimming. They would prey mainly on ‘Sea Cucumbers’ (Echinoderm’ animals, thus related to Starfish & Sea Urchins), which are often relatively abundant at those levels and are ‘deposit feeders’ that extract micro-organisms & organic debris from ingested seabed material: The swimming ability is for moving longer distances to seek their specific prey, instead of just wandering around in the hope that enough food turns up as the larger type presumably does most of the time.
(Potential food supplies at that level are probably too low to support viable populations of Trilobites that deposit-feed directly…)
Type Three
The adults of these would live around the seabed’s ‘hydrothermal vents’ in tectonic ‘rifts’, where the geothermally-heated water can reach very high temperatures. Like the other animals living in those environments they would rely directly or indirectly for food on the chemosynthetic Bacteria which thrive in the mineral-rich waters that rise from within the Earth’s crust there, but their larvae would possibly still be planktonic. Forms adapted for living around vents rather than just seeps would obviously have to have evolved greater tolerance for high temperatures, and probably have some kind of temperature-checking sense (such as eyes adapted to see in infra-red?) as well. Those environments seem to support few significant predators in RL, so the local Trilobites’ armour might have become reduced in thickness and/or in mineralisation. Adaption for relatively low oxygen levels would probably be useful here, as might a greater tolerance for hydrogen sulphide.
Subtype ‘Three A’ simply scrapes bacteria from surfaces, and might have some of its legs adapted for this purpose.
Subtype ‘Three B’ has some of its legs adapted to form a ‘net’ or ‘sieve’ that filters floating bacteria out of the water, if[/]i the currents around the vents & seeps actually allow adequate concentrations of that food-supply [i](which I need to check before confirming that this variety is actually possible…).
Subtype ‘Three C’ actually carries some of the Bacteria as symbiotes, living in pouches of some kind in its own structure, however the RL fossil Trilobites that are thought to have had symbiotic bacteria managed this (which one source says was in specialised structures attached to their gills). It might also consume some bacteria scraped from surfaces, to supplement the symbiotes’ efforts.
Subtype ‘Three D’ takes a more indirect route to that foodstuff: It is an external parasite on the ‘Giant Tube Worms’ (‘Vestimentifera’) that also live at some such sites and that themselves rely on symbiotic bacteria for their nourishment. The adults of this variety would probably be smaller than those of any of the other subtypes listed here.
Type Four, subtypes ‘Four A’ to ‘Four D’: These are similar to Type Three, but live around the cooler ‘methane seeps’ instead and therefore haven’t evolved as great a tolerance for heat: Some of them might also colonise whale carcasses, probably arriving there after major scavengers such as the members of Type One have finished. (Type Three is probably descended from earlier members of Type Four.)
_______________________________________________________
More References
https://en.wikipedia.org/wiki/Giant_isopod
https://en.wikipedia.org/wiki/Whale_fall
https://en.wikipedia.org/wiki/Sea_cucumber
https://en.wikipedia.org/wiki/Hydrothermal_vent
https://en.wikipedia.org/wiki/Cold_seep
(Vestimentifera =) https://en.wikipedia.org/wiki/Siboglinidae