zoocreation


A biblical History of Sea Cows



Dugongs and Manatees After the Flood



Chad Arment (2022)





The living sea cows of the order Sirenia, three recognized species of manatees (Trichechus) and one species of dugong (Dugong), are the last survivors of an extraordinary and diverse group of marine mammals. All sirenians, past and present, have been grazing mammals, thus the epithet ‘sea cow.’ Freshwater species browse(d) on the aquatic plants found in rivers, estuaries, and lakes, while marine species graze(d) on seagrasses or kelp. Some of the earliest sirenians were possibly amphibious rather than fully aquatic, and feeding strategies throughout time include both generalist and selective browsing (Domning 2001b).


Within the creation model, sea cows offer an interesting take on biogeographical expansion after the Flood. After all, being aquatic, though air-breathers, sea cows were outside the Ark and survived the turbulent Flood. So there was no forced genetic bottleneck of only a single pair surviving the Flood within their baraminic kind or kinds. This means that the immediate post-Flood sirenians could potentially have included multiple genera or even families within a single baraminic kind. After all, the original created sea cows had a significant amount of time to multiply and differentiate as they ‘filled the earth.’





Summary of Post-Flood Sea Cow Diversification



The First Sea Cows



One evolutionary biologist has noted (Domning 2001b), “Although sirenians are thought to have arisen in the Old World . . . they seem to have spread quickly to the New World end of the Tethys Seaway, where their actual fossil record begins in the late Early Eocene of Jamaica,” but it wasn’t long before Eocene fossils in the Old World were discovered. Evolutionists attempt to tie sirenians in with elephants and kin (the proboscids) and a few other fossil groups in the clade Tethytheria, but there are no specific ‘ancestral’ fossils confirming such a common relationship. That’s just evolutionary speculation. As Heritage and Seiffert (2022) noted, “a temporal comparison of the earliest known sirenian fossils to the supposed age of the Sirenia-Proboscidea lineage split . . . suggests that the first 10 million years (or so) of the order’s evolutionary history has not yet been documented by fossils. Conversely, the middle Eocene to Recent fossil record of sea cows is quite good . . .”


For creationists, we can note the Eocene as the first appearance of fossil sirenians, likely post-Flood, and recognize that there probably aren’t any sirenians found in direct Flood deposits. This may simply be due to how the Flood occurred: some ecosystems (like those with significant human populations) were likely wiped out without a trace.


But unlike the evolutionary perspective, who look at the Eocene as an epoch straddling over 20 million years, for a creationist the Eocene is very near the start of the post-Flood period. (How near, still requires discussion, particularly as it may not be consistent across all continents.) But during the Eocene, at least 13 different genera of sirenians make their appearance. Those are in three of the four recognized families of the order Sirenia: the Prorastomidae, the Protosirenidae, and the Dugongidae. An additional eight genera show up in Oligocene deposits, though seven are in the Dugongidae and one is the first of the family Trichechidae (manatees). What does this suggest?



Early Sea Cow Diversity



The first thing it suggests is that sirenians were a highly diverse group prior to the Flood. Were all sirenians part of a single baraminic kind? That’s not as clear. A number of ‘popular’ creationists seem to have difficulty with the idea of large vertebrates showing limb variation. (Yet they don’t seem to object to amphibian or reptile baraminic kinds showing that degree of variation.) While modern day sirenians only have their front flippers, some fossil sirenians were quadrupedal, and may have been more amphibious than fully aquatic. So, it’s possible that each of the four families of sirenians were distinct and represented separately created baraminic kinds. It’s also possible that they represent branching from 2000 years or so of pre-Flood diversification and morphological divergence within fewer kinds, or even within a single baraminic kind.


It should also be noted that these Eocene sirenians are not showing up in the very same area. These fossils likely show where small groups of sirenians managed to disperse after surviving the turbulence of the Flood.


After this initial Eocene period, two families that survived the Flood soon disappear, while the family Dugongidae begins to diversify. Not every pre-Flood organism survived long in the post-Flood environment. Climate and habitats continued to change, as they hadn’t yet stabilized. Sea cow distribution was dependent on healthy seagrasses and other aquatic plants. The dugongids took advantage of waning competition to move into new habitats, and were able to adapt to different feeding niches in the post-Flood world.



West Indian Manatee (Robert Bonde / USGS)



Eocene



Three recognized families appear in the Eocene: Prorastomidae, Protosirenidae, and Dugongidae. A couple genera of undetermined family also are present. Sobrarbesiren, for example, appears to have been a sister taxon of the Dugongidae (Díaz-Berenguer et al. 2018). Species were mostly smaller (‘pig-sized’) than our modern West Indian manatee (Suarez et al. 2021).


It is important to note that each of these groups had distinctly different limb arrangements and locomotion. Prorastomids, protosirenids, and Sobrarbesiren were all quadrupedal, though dissimilar in swimming capability and movement. Dugongids were fully aquatic, lacking hindlimbs (Díaz-Berenguer et al. 2020). This variability could certainly point to separate baraminic kinds, but it could also point to a much wider pre-Flood diversification within fewer baraminic lineages. The diversity would allow multiple kinds of sirenians to take advantage of different ecological niches in the same area.


Prorastomidae: The Prorastomidae included two genera: Prorastomus and Pezosiren. They were fully quadrupedal, but have morphological characteristics suggesting a hippopotamus-like existence, preferring shallow aquatic habitats with lots of vegetation to eat (Domning 2001a; Savage, Domning, and Thewissen 1994). These were coastal and estuarine habitats (Benoit et al. 2013). Hautier et al. (2012) noted, “the postcranial skeleton of Pezosiren indicates that it was capable of supporting its own body weight on land, whereas on the other hand its pachyosteosclerotic ribs, retracted external nares, and lack of paranasal air sinuses show that it was well adapted for aquatic life.” Díaz-Berenguer et al. (2020) concurred: “The most complete prorastomid, Pezosiren portelli . . . combines aquatic skeletal characteristics, such as retracted nares and pachyosteosclerotic bones, with features of terrestrial mammals, such as a multivertebral sacrum, a weight-bearing sacroiliac articulation and well-developed hindlimbs.” Prorastomids had “very narrow, forceps-like, nearly undeflected mandibular symphyses [that] are interpreted as adapted to selective browsing, possibly on surface-growing as well as bottom-dwelling plants” (Domning, Hill, and Sorbi 2017).


Protosirenidae: Protosirenids (or at least Protosiren) were quadrupedal with well-developed but reduced hind limbs. If they moved on land, it was probably like a seal or walrus (Díaz-Berenguer et al. 2020). Protosirenids were adapted “toward grazing on meadows of bottom-growing seagrasses: the cropping apparatus is broadened,” while incisors and canines play little role and may be significantly reduced in size (Domning, Hill, and Sorbi 2017). Zalmout and Gingerich (2012) noted, “Protosiren had larger tusks, lacked rib pachyostosis, and had ribs articulating via a cartilaginous connection to the thoracic vertebrae. Large tusks suggest feeding on rhizomes, and the unique rib articulations suggest breathing and buoyancy different from other sirenians. If the ribcage was collapsible, this may have enabled Protosiren to feed in deeper water, and retention of functional hind limbs may have enabled Protosiren to move while submerged feeding on the seabed.”


Dugongidae: Eocene dugongids were “already fully aquatic animals, which lack external hindlimbs and used the tail as the main propulsive element for swimming” and “only vestigial innominate bones and femora are known for this family.” (Díaz-Berenguer et al. 2020). Dugongids like Eosiren and Eotheroides had closer-packed ribs than other Eocene sirenians and may have inhabited shallower water “where it was easier to come to the surface to breath” (Zalmout and Gingerich 2012). Zalmout and Gingerich (2012) also noted, “Sea grass preserved as leaf impressions is direct evidence of the shallowness of Tethyan shelf waters where Eocene sirenians are found in Wadi Al Hitan and elsewhere.”


Sobrarbesiren was a bit larger sirenian for the Eocene, about 2.7 meters in length (Díaz-Berenguer et al. 2018). It was fully quadrupedal but probably could not walk on land. Microanatomical features “suggest an exclusively aquatic lifestyle,” as the bones were likely brittle and not suited for terrestrial locomotion (Díaz-Berenguer et al. 2020). Díaz-Berenguer et al. (2018) suggested this represented a stage between fully mobile quadrupeds and sirenians lacking hind limbs, but we find all ‘stages’ at approximately the same time after the Flood. Now, dugongids did reduce their limbs from practically vestigial to fully gone, so limb reduction is certainly possible. Díaz-Berenguer et al. (2018) also suggested that Sobrarbesiren could potentially be ancestral to the Trichechidae, but the latter may also be an early offshoot of early dugongids.


The Chambi Sea Cow: The available fossil material didn’t allow for placement in a recognized family, but evolutionists believe that this is the oldest fossil sirenian, found in a freshwater deposit in Tunisia (Benoit et al. 2013). It had a number of ‘primitive’ sirenian traits, but demonstrated morphologically that it was well-adapted for an aquatic lifestyle. For example, it could likely hear underwater.




Eocene Sea Cows





1 Prorastomidae

2 Chambi Sea Cow

3 Sobrarbesiren

4 Protosirenidae

5 Dugongidae



Eocene Key:


Prorastomidae

1A Prorastomus and Pezosiren, 1B gen. et sp. indet., 1C gen. et sp. indet.


Fam. indet.

2 Chambi sea cow

3 Sobrarbesiren


Protosirenidae

4A Ashokia, 4B Libysiren, 4C Protosiren, 4D gen. et sp. indet.


Dugongidae: Basal

5A Anisosiren, Paralitherium, and Sirenavus, 5B Eosiren, 5C Eotheroides, 5D Halitherium (nomen dubium), 5E Prototherium


(Bajpai, S., et al. 2006; Bajpai, et al. 2009; Balaguer and Alba 2016; Benoit et al. 2013; Díaz-Berenguer et al. 2018; Diedrich 2013; Domning 2001; Domning, Heal, and Sorbi 2017; Hautier et al. 2012; Savage, Domning, and Thewissen 1994; Kordos 2002; Samonds et al. 2009; Zalmout and Gingerich 2012; Paleobiology Database)


Note: Maps very roughly approximate continental position after the Flood. [Map background revised, CC BY-SA 4.0 Crates]



Sobrarbesiren



Díaz-Berenguer et al. 2018, CC-BY 4.0



oligocene



By the Oligocene, the Prorastomidae and Protosirenidae have disappeared. Only the Dugongidae continue to be found in Oligocene deposits, but two different subfamilies begin to differentiate from within the numerous dugong genera (Domning 1997): the Dugonginae and the Metaxytheriinae. (There are a number of ‘basal’ dugongs that continue to show up in the Oligocene, but most of those disappear by the Miocene.) Another sirenian also shows up, Anomotherium, the first true trichechid. An offshoot of Sobrarbesiren’s lineage? In any case, it is part of the subfamily Miosireninae which differs substantially from the modern manatee’s lineage. Additional fossil material will likely be necessary to understand manatee development during this time.




Oligocene Sea Cows





1 Dugongidae: Basal

2 Dugonginae

3 Metaxyteriinae

4 Miosireninae



Oligocene Key:


Dugongidae: Basal or Undetermined

1A Caribosiren, 1B Eosiren, 1C Kaupitherium, 1D Lentiarenium, 1E Priscosiren, 1F Prototherium


Dugongidae: Dugonginae

2A Bharatisiren, 2B Callistosiren, 2C Crenatosiren, 2D Dioplotherium, 2E Halitherium, 2F ?Halitherium, 2G Italosiren, 2H Stegosiren


Dugongidae: Metaxytheriinae

3A Metaxytherium


Trichechidae: Miosireninae

4A Anomotherium


(Diedrich 2013; Domning and Beatty 2019; Gol’din, Kovalchuk, and Krakhmalnaya 2019; Vélez-Juarbe and Domning 2014a; Vélez-Juarbe and Domning 2014b; Vélez-Juarbe and Domning 2015; Voss, Berning, and Reiter 2016; Voss, Sorbi, and Domning 2017; Paleobiology Database)


[Map background revised, CC BY-SA 4.0 Crates]



miocene



Dugongidae: During the Miocene the ‘basal’ dugongs were starting to disappear, while the distinctive subfamily Dugonginae showed expansive diversification. This period was, in fact, peak diversity for dugongs. They were also spreading outside the former Tethys Seaway, into both sides of the Pacific. Vélez-Juarbe et al. (2012) noted that Dioplotherium and Metaxytherium found in Miocene Argentina probably dispersed along the coastline, following seagrasses into the inland Paranense Sea. Bianucci et al. (2006) noted that a dugong tooth was found in the Upper Miocene sediments of Chile. This suggested “warm shallow water with seagrass beds” to the authors and other fossils with tropical and subtropical affinities corroborated this idea.


Bharatisiren was the first fossil dugongine from the Indian Ocean (Bajpai and Domning 1997). A speleological expedition to a cave in the remote Hindenburg Range of the New Guinea Highlands, Papua New Guinea, recovered sirenian bones, genus undetermined (Fitzgerald et al. 2013). Several parts of New Guinea were underwater at that time, and significant geological activity (including mountain formation) was yet to come (Toussaint et al. 2021).


The Old World Rytiodus appears closely related to the Pliocene Corystosiren of the New World, with an undescribed Miocene taxon from South Carolina possibly intermediate (Domning 1990), so trans-Atlantic migration seems to have continued during this period. Domning (1989b) suggested that Dioplotherium allisoni could be “directly ancestral to Xenosiren,” though Bajpai et al. (2010) thought Xenosiren might have come from Bharatisiren or Kutchisiren. Rytiodus (Libyan specimens), Corystosiren, and Xenosiren all had large blade-like tusks that may have been used to dig large, tough seagrass rhizomes (Domning and Sorbi 2011).


Diversification led to diverse ecological systems, where multiple sirenian forms were found. Sympatric sirenian assemblages were not random—there were discrete morphological and resource partitions, suggesting different foraging areas and feeding behavior (Vélez-Juarbe et al. 2012). In the Old World, large-tusked Rytiodus is often found in deposits with small-tusked Metaxytherium (Domning and Sorbi 2011). Samonds et al. (2019) noted that Madagascar had “a contemporaneous multispecies sirenian fauna, as is commonly seen elsewhere in the world,” while De Toledo and Domning (1989) wrote, “Miocene sirenian faunas on the Atlantic coasts of South America displayed a diversity comparable to those in North America.”


Metaxytheriinae: The genus Metaxytherium was widespread during the Miocene, with significant populations in the Mediterranean and the Caribbean. Domning and Pervesler (2012) suggested the “European and North African Miocene and Pliocene Metaxytherium formed a single, anagenetically-evolving lineage”, with a typical species like M. medium “considered an ecological generalist among sirenians, inhabiting tropical to warm temperate shallow marine waters and feeding on seagrasses.” Metaxytherium serresii, was found from Late Miocene to Early Pliocene in France, Libya, and Italy, with a reduction in body size due to “Messinian disturbances of salinity and sea level [that] reduced the quality, quantity, and/or diversity of the seagrass forage” (Carone and Domning 2007).


In the New World, from the Miocene to Early Pliocene, Metaxytherium calvertense had a very extensive range. “The Central American Seaway, open during the Miocene, permitted M. calvertense to range throughout the continuous zone of warm, shallow marine waters extending from Maryland to Peru” (De Muizon and Domning 1985). It wasn’t long before they disappeared, however. As Domning (1988) noted: “It may be . . . that immigration of competitively superior South American manatees into North America by the late Hemphillian led to extinction of the dugongids; or the manatees may simply have moved into a vacuum left by the dugongids’ demise. In any case, Metaxytherium followed into extinction several other West Atlantic dugongid lineages that had similarly and independently evolved strongly downturned spouts suited to bottom-feeding. However, the abundant seagrasses on which such animals undoubtedly fed persist in Florida to this day. Why bottom-feeding so often proved to be an evolutionary dead end for them remains an unresolved paradox.”


Metaxytherium appears to have left a genetic legacy, though, De Muizon and Domning (1985) suggested, as Metaxytherium may have given rise to Dusisiren and the Hydrodamalinae in the Pacific. Aranda-Manteca et al. (1994) noted, “Dusisiren appears to have evolved in the eastern North Pacific from Metaxytherium,” with Metaxytherium arctodites appearing to be a sister taxon of Dusisiren, as it shared derived characters with the hydrodamalines that aren’t found in other Metaxytherium.


Hydrodamalinae: Takahashi et al. (1986) wrote, “Taken at its face value, the Japanese record now indicates that hydrodamaline sirenians first dispersed northward and westward from California in the Late Miocene, after they had evolved the degree of cold-adaptation represented by Dusisiren dewana” as that species could apparently tolerate colder water than D. jordani. There was also morphological change in dentition, with representative stages including the toothed Dusisiren jordani, the intermediate D. takasatensis, and the toothless Hydrodamalis cuestae (Kobayashi et al. 1995).


Trichechinae: Potamosiren first showed up in Miocene Columbia (Suarez et al. 2021): “The early Miocene appearance of trichechines coincides geographically and temporally with the onset of the Pebas Mega-Wetland System. . . .” Trichechine manatees were likely confined to freshwater ecosystems due to the presence of multispecies dugongid communities previously established along the coastlines. After the dugongs in the region disappeared, manatees were able to return to marine environments and expand their range.




miocene Sea Cows





1 Dugongidae: Basal

2 Dugonginae

3 Hydrodamalinae

4 Metaxytheriinae

5 Trichechinae

6 Miosireninae



Miocene Key:


Dugongidae: Basal

1A Halitherium, 1B Indosiren, 1C Lentiarenium, 1D Miodugong, 1E Prohalicore


Dugongidae: Dugonginae

2A Bharatisiren, 2B Culebratherium, 2C Dioplotherium, 2D Domningia, 2E Kutchisiren, 2F Nanosiren, 2G Norosiren, 2H Rytiodus, 2I Xenosiren


Dugongidae: Hydrodamalinae

3A Dusisiren, 3B Hydrodamalis


Dugongidae: Metaxytheriinae

4 Metaxytherium


Trichechidae: Trichechinae

5A Potamosiren, 5B Ribodon


Trichechidae: Miosireninae

6 Miosiren


(Domning 2001; Williams and Domning 2004; Paleobiology Database)


[Map background revised, CC BY-SA 4.0 Crates]



pliocene



The sirenian fossil record for the Pliocene is not as abundant as for the Miocene, but there are a few points to note.


Dugonginae: Two flat-tusked dugongs co-existed in the Caribbean during the Pliocene, Corystosiren and Xenosiren. Domning (1990) noted, “how food resources might have been partitioned between these two is not easy to explain.” Of course, for the creationist model, this period didn’t last long. Pledge (2006) reported an Early Pliocene dugong jaw found in the Loxton Sands of South Australia. This is the earliest true dugong from Australia, and may have been an early Dugong or closely ancestral. The New World dugongine Nanosiren (Miocene and Pliocene) species were the “smallest known post-Eocene sirenians” (Domning and Aguilera 2008).


Metaxytheriinae: Metaxytherium subapenninum was the last sirenian of the Mediterranean Basin and the last and most derived Metaxytherium species (Sorbi et al. 2012). Climatic cooling had apparently led to an increase in body size and tusk size (apparently to obtain more nutritious rhizomes). In contrast, hydrodamalines also grew large, but adapted to algae in cold waters, surviving into historic times.





pliocene Sea Cows





1 Dugonginae

2 Hydrodamalinae

3 Metaxytheriinae



Pliocene Key:


Dugongidae: Dugonginae

1A Corystosiren, 1B Dioplotherium, 1C Dugongid, undescribed genus, but similar to Dugong, 1D Dugongid, possibly a very early Dugong, 1E Nanosiren


Dugongidae: Hydrodamalinae

2A Dusisiren, 2B Hydrodamalis


Dugongidae: Metaxytheriinae

3 Metaxytherium


(Domning 2001b; Pledge 2006; Sorbi et al. 2012; Frederico, Jr., and McLain 2021; Paleobiology Database)


[Map background revised, CC BY-SA 4.0 Crates]



pleistocene



Trichechinae: The Pleistocene saw the development of modern manatees. Perini et al. (2020) noted, “At some point during the Pleistocene, the ancestral stock of the three modern species was distributed along the northern South American coast, Caribbean, Gulf of Mexico, and, perhaps, the large South American rivers systems. During the Pleistocene, the eastern Amazon became savannized . . . losing the capacity to support environments suitable for manatees, but the western Amazon remained largely unchanged, restricting the freshwater manatee populations there.” This may have occurred several times, following significant changes to South American river courses and wetland formation (De Souza et al. 2021), isolating different populations and promoting endemism.


Domning (2005) noted that “early Pleistocene manatees from Florida are more similar to modern T. m. manatus than the late Pleistocene ones [T. m. bakerorum] are.” This is likely due to climatic patterns that set up barriers for gene flow, promoting the endemic formation of the bakerorum subspecies, then removed the barriers, allowing that genotype to be swamped. Domning also suggested that African manatees probably originated from waif dispersal of manatees from the New World. He pointed to such evidence as: a) manatees clearly go back to the Miocene in the New World, b) early Pleistocene manatees from Florida suggest a plausible structural ancestor for African manatees, and c) a nematode found in African manatees appears to be more specialized than a similar species found in New World manatees.


The most significant development in manatees was the dentition. Trichechus has ‘horizontal tooth replacement,’ which is lacking in the earliest true manatee (O’Shea 1994), where, “In each quadrant of the mouth, new molars are developing in the posterior-most portion of the jaw in a continuously active and developing crypt” (Beatty et al. 2012). “Manatees possess only pre-molars and molars (one row on either side of the jaw), but these are continuously replaced by new teeth sprouting at the rear of the row—rather like wisdom teeth—and moving forward. The worn-down front teeth drop out, and the bony tissue separating the tooth sockets continuously breaks down and re-forms to allow the new teeth to move forward at roughly one or two millimeters per month” (O’Shea 1994). So, up to 30 molars develop over the manatee’s lifetime in each of the four quadrants, with the molars erupting posteriorly, shifting forward like a ‘conveyor belt’, until they fall out the front over time. What triggered this development is unknown, though it may involve sediment interaction or abrasive plant fodder. “In contrast to the specialized seagrass grazing of dugongs, manatees are considerably more generalized mixed-feeders, with Trichechus manatus latirostrius reported to consume over 60 plant species in Florida” (MacFadden et al. 2004). Within the Trichechidae, Ribodon shared a number of dental features with Trichechus; not so many with Old World miosirenians. “The geographic gaps between the European Miosireninae and largely neotropical Trichechinae indicate a large gap in the fossil record of this group, one that probably contains many of the anatomical transitions identified here” (Beatty et al. 2012). A plausible developmental lineage would be Potamosiren to Ribodon to Trichechus.


Hydrodamalinae: Hydrodamalis (which included the now-extinct Steller’s sea cow), was completely toothless, and instead “used a pair of broad cornified horny pads to masticate kelp (algal seaweeds)” (Springer et al. 2015). Hydrodamalis gigas was the largest recent sirenian, with one female measured at 7.52 meters (Forsten and Youngman 1982). Hydrodamalines lost both teeth and phalanges. Steller’s sea cow was said, from written accounts, to have had bark-like skin and a thick layer of fat. This led to extreme buoyancy, and it was apparently unable to submerge. In recent genetic research of Steller’s sea cow skin, several genes have been identified that suggested adaptation to cold aquatic environments, forming exceptionally thick blubber and inactivating lipoxygenase genes, which could cause a ‘thick, hyperkeratotic epidermis’ (Le Duc et al. 2022).




pleistocene Sea Cows





1 Trichechinae

2 Hydrodamalinae



Pleistocene Key:


Trichechidae: Trichechinae

1 Trichechus


Dugongidae: Hydrodamalinae

2 Hydrodamalis


(Domning 2001b; Bell et al. 2020; Furusawa and Kohno 1994; Mattioli and Domning 2006; Perini et al. 2020; Williams and Domning 2004; Paleobiology Database)


[Map background revised, CC BY-SA 4.0 Crates]



Dugong dugon



Musée zoologique de Strasbourg, by Ji-Elle (CC BY-SA 3.0)



Hydrodamalis gigas



Jardines des Plantes, by Nicolas Venner



Trichechus manatus



Daniel Giraud Elliot, 1904



Trichechus manatus



Sklmsta (PD-0)



holocene



Today we have one living species of Dugong, three species of manatee (Trichechus) and a recently extinct species, Steller’s sea cow. Besides their recognized distribution, manatees have been noted in the Pacific, the result of a) intentional introduction in an aquatic plant control program that was soon abandoned, and possibly b) immigration through Panama Canal locks (Guzman and Real 2022).


An Ohio manatee: Williams and Domning (2004) reported on a manatee bone found in gravel pit near Springfield, Ohio, radiocarbon dated at about 2,000 years B.P. There was no indication of wear, so likely no post-mortem fluvial transport. This suggests it was possibly a Holocene alluvial deposit, or there may have been human intervention in bringing it here from a nearby river. Another manatee bone, likely Pleistocene, was found on a gravel bar in the Mississippi River in Arkansas, supporting the idea that the Ohio animal traveled up the Mississippi into the Ohio River and was possibly caught and trapped in the drainage basin after a season of flooding. This particular specimen interests me, as I’m within an hour or so from the quarry it was found (Springfield Sand and Gravel Co., right behind the Clark County Fairgrounds). It’s now owned by the city, but is filled with water, so no further discoveries are likely. It may simply have been a wanderer, as we sometimes see the occasional manatee swim as far as the Chesapeake Bay during the summer months.




Modern Sea Cows





Figure from Heritage and Seiffert (2022); CC-BY 4.0



Conclusion



The loss of so many kinds of interesting sea cows is one of the tragedies of living in a fallen world. We really don't know the extent of pre-Flood sirenian diversity, as we only have small glimpse into what survived the Flood. As the warm post-Flood waters started to cool, it was the dugongs (and the ancestral manatees, whatever they were) that managed to adapt to continuous climatic change and take swift advantage of the expanding seagrass habitat that developed along continents as they continued drifting apart. Eventually dugong diversification peaked and declined, and manatees began to expand out of their South American wetland origin and into marine coastal habitats. One dugong lineage moved into the cold North Pacific waters as it adapted morphologically to the kelp forest, only to disappear forever in the 1700s. Today, only one dugong and three manatee species survive. Conservation efforts have led to moving the West Indian manatee from 'endangered' to 'threatened' status, and conservationists continue to work with local people groups in other regions where sea cows live. As part of the Dominion mandate, Christians are called to recognize sea cows as God's creation, and wisely use our resources and judgment to allow these lineages to thrive and continue bringing glory to the Creator.




Dugong in the Red Sea



Julien Willem (CC BY-SA 3.0)



West Indian Manatee



Robert Bonde / USGS



West Indian Manatee



Everglades National Park Service



West Indian Manatee



Nick Aumen / USGS



Update 9/11/2022



I was reminded that sirenians were included in Todd C. Wood's 'Survey of Cenozoic Mammal Baramins' in the 2018 ICC Proceedings. Wood determined that prorastomids and protosirenids were excluded from the dugong-manatee baramin. We still don't know whether Sobrarbesiren is included, as that was only described in 2018. So the evidence currently suggests there were at least three sirenian baramins after the Flood, and possibly more. If Sobrarbesiren is excluded, then that means that it is also excluded as a possible ancestor for manatees, because manatees and dugongs cluster together in Wood's statistical baraminology matrix.


See 'A Survey of Cenozoic Mammal Baramins'

references



Aranda-Manteca, F. J., D. P. Domning, and L. G. Barnes. 1994. A new Middle Miocene sirenian of the genus Metaxytherium from Baja California and California: Relationships and paleobiogeographic implications. In: Berta, A., and T. A. Deméré, eds. Contributions in Marine Mammal Paleontology Honoring Frank C. Whitmore, Jr. Proceedings of the San Diego Society of Natural History 29: 191-204.


Balaguer, J., and D. M. Alba. 2016. A new dugong species (Sirenia, Dugongidae) from the Eocene of Catalonia (NE Iberian Peninsula). Comptes Rendus Palevol 15(5): 489-500.


Bajpai, S., and D. P. Domning. 1997. A new dugongine sirenian from the Early Miocene of India. Journal of Vertebrate Paleontology 17(1): 219-228.


Bajpai, S., et al. 2006. Eocene and Oligocene sirenians (Mammalia) from Kachchh, India. Journal of Vertebrate Paleontology 26(2): 400-410.


Bajpai, S. et al. 2009. A new middle Eocene sirenian (Mammalia, Protosirenidae) from India. N. Jb. Geol. Paläont. Abh. 252: 257-267.


Bajpai, S., et al. 2010. A new fossil sirenian (Mammalia, Dugonginae) from the Miocene of India. N. Jb. Geol. Paläont. Abh. 258(1): 39-50.


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