Writing: Input Wanted Looking for story advice on ancient aquatic reptile breeding grounds

[DaveC426913]

I'm looking to pick the brains for a fantasy story of someone who knows a little about how ancient aquatic reptiles (~65Mya) might have migrated to breeding grounds in ancient Atlantic Ocean and its shores.

The premise is that such creatures, last seen 65 million years ago, managed to survive through the ages on the shores of mid-Atlantic islands - now gone - and ended up in (relatively) modern times. The questions are mostly about how their migration patterns for breeding might have occasionally switched to inland waterways (even if such waterways didn't exist until after the glaciers came and went).

The heart of the question is: why would such creatures breed in one remote place for generations, and then, every few millennia or so - switch up their breeding grounds to a different place? Like turtles going to the Galapogos Islands for a thousand gneratinos and then every millenium, return to the shores of South America. That sort of thing.

Is there any precedent in the animal kingdom for changing up breeding waters on a long cycle?

There's more to this, I'll explain the rest of the premise - I'm just putting this out as a feeler to see if there's anyone willing "bite".

I'm leveraging my paleo-biologist sister to see what she might come up with, but she is a hard scientist, and may struggle with the ... er ... artistic licencial contrivances ... of a fantasy story.

 

[DaveC426913]

What if their food source waxed and waned over centuries, causing a shift in the feeding - and thus breeding - grounds? Or other environmental factors, such as water temp, magnetic pole flipping or other changes were the cause of the long-term cycles?

 

[berkeman]

Paging the obvious PF subject matter expert @BillTre

(well, at least for current aquatic animals)...

 

[BillTre]

Not entirely clear on what you're after here.
Nevertheless you may find some of this useful:

• Breeding grounds can persist for very long times. Eels are an example. Possibly breeding in the center of the Atlantic since continental drift opened up the Atlantic.
• The long flights of birds to some breeding grounds may be due to the seasonal availability of food in those locations (there may be few predators for intermittent large potential food resources.

Unless the nature of their eggs were to change, reptiles would have to return to land to breed. Alternatively they could not lay their eggs and release their offspring after they developed and hatched internally. Fish have done this several times. Its called ovoviviparity.

When Africa and South America split the new world and old world monkeys were separated and then evolved in their own different directions.
There was a similar split of cichlid fishes in the two continents. However their evolution separation was delayed for quite a while. The cichlids are freshwater fish and normally would not be able to migrate between the two continents, however both the Amazon and Congo rivers both flowed into the opening south Atlantic providing a sufficiently fresh water path between the two that the fish could make that migration. See https://en.wikipedia.org/wiki/Cichlid, the evolution section.

Among evolving fish there have been many changes in habitat between freshwater and salt water living. These have often been accompanied by radiations of new species in the new environments. In most cases where they bred would change, but maybe not always.

There are some small fish in Hawaii (Hawaii is a fish impoverished place due to its extreme isolation) that migrate (I believe) from salt water around Hawaii, up waterfalls on vertical cliffs, to breed. their pelvic fins are able to form a suction cup in order to do this.

According to Google, here are some known changes in migration patterns:

• Blackcap (Sylvia atricapilla):
  A central European population of this bird evolved a new migration route to the British Isles within a 30-year period, demonstrating rapid, genetically-programmed adaptation.

• Monarch Butterflies:
  The introduced Australian population has developed a migratory pattern that differs by 180 degrees in direction and 6 months in timing from their North American counterparts, showing how migration can change quickly.
• Hummingbirds:
  As glacial ice melted, various species, including hummingbirds, gradually expanded their breeding ranges northward over time.
• Spotted Owls:
  Mountain populations of spotted owls have evolved an altitudinal migration, moving to lower elevations during winter snows, while non-mountain populations of the same species exhibit different migration patterns.
• Wildebeest Migration:
  The Great Wildebeest Migration is a cyclic journey that follows the availability of fresh grazing land and water from the Serengeti to the Masai Mara, demonstrating a pattern of adaptation to seasonal resource availability.

 

[DaveC426913]

Not entirely clear on what you're after here.

I will elaborate later today.

 

[DaveC426913]

OK, here is the tentative premise:

This is a prequel to a fantasy story I've already finished (but have not published), called Mosasaur Summer. It's about sea monsters on Toronto's Centre Island beaches. In Mosasaur Summer, the arrival of the Mosas on Toronto's beaches is never explained, and I thought I might like to go back and revisit that from a different viewpoint. I want to touch a little on how it came to be that Mosasaurs started coming up the St. Lawrence River (once it existed, that is, since it's only been around since the last Ice Age, 10,000 years ago) to their breeding grounds in the Great Lakes (which are also young).

This is fantasy, mind, so it doesn't have to be scientifically accurate, as long as it's plausible to my (non-paleo) readers.

So: 65 million years ago, during the heyday of Mosasaurs, the Atlantic Ocean was much, much narrower than today. There were large landmasses in the Atlantic, where the Mid-Atlantic ridge is (and stories of these islands might have been carried down through the ages to turn up as myths about the lost continent of Atlantis, before they disappeared under the waves. This Atlantis won't be the Mecca of Wonders legends tell of, it's merely a land where some peoples lived as recently as, say, 40,000 years ago.)

So, my idea revolves around the Mosasaurs, who in my world, gave birth to live young - or are perhaps ovoviviparitous (giving birth to live young that hatch from internal eggs). They used beaches and shallow bays to mate and breed (they are, after all, air breathers, like turtles and other reptiles).

Their native breeding grounds would have been the beaches of these Atlantic Islands but, as the land masses sank, they had to move to new their breeding grounds or perish.

I'm trying to figure out a few things about how this shift might come about in the required timeline. The first 65 millions years is not the hard part, it's the last 50,000 years I'm trying to line up. It should be long enough ago that these mid-ocean island chains did not come to light of modern ocean-going civilizations (except as legend), yet recent enough to introduce the critters to a new land that was sporadically covered in glaciers until recently.

- As mentioned, the St.Lawrence and the Great Lakes didn't even exist until 10,000 years ago, so I have to figure out how to transition their breeding grounds over, about 30,000 years. Perhaps the last of the Atlantean Islands slid under water 40,000 or so years ago, recently enough that mentions of them might have been carried down in oral legends.

- There is a "lie" in my story (i.e. I made it up) that the Mosas only come up the St. Lawrence every generation of generations or so - I dunno - every thousand years - or something like that. (If they returned every year, they would leave too big a telltale footprint both in our paleo-geology records as well as in native North American cultural history.) So, the question I have to address is why would a species breed in one place for, you know, 900 generations, and then one year, visit a different breeding site? Is there any such precedent in the animal kingdom?

(Update: yes, there is.)

And lots of ideas have come forth: from realistic food source waxing and waning to fanciful geomagnetic disruptions - there was a temporary and partial magnetic pole reversal around 40,000BC (Lechamps Excursion). Perhaps enough to disrupt their migration temporarily before they recovered.)

- I'm toying with playing up the fact that there was once a sixth Great Lake "Lake Agassiz" (true!) that was far, far larger than the current lakes combined than occupied most of what is now Manitoba. Perhaps big enough for ocean-dwelling reptiles to use as a "summer vacation" spot or something. The lake is gone now, but their migration patterns might still be bringing them up this way, which is why they end up in the Great Lakes. (They are following the salmon up-river, which is what the newborns and juveniles feed on, before returning to the ocean).

Unfortunately, liek everything else in Canada, Lake Agassiz also didn't exist until 10,000 years ago, so that doesn't really help as a plausible "transitionary migration" pattern.


Ultimately I'm trying to fit the breeding patterns and migratory routes of (fictional) Mosasaur descendent (they've had 65 million years of evolution) into known geology timelines withjout having them encountered by modern ACE (After Common Era) humans.


TL;DR:

Here is the real plot hole I've painted myself into a corner with. These ancient reptiles have shown up in the present day. That's the premise of the ... er ... periquel.

But only this year. Where did they breed last year? Or any other year in the last 10 or 20 millennia since their Atlantean breeding ground sank between the waves? How have they not shown up in more recent records? It stretches plausibility to breaking to pretend they've been breeding on the shores of some North Atlantic island throughout all of recorded history - and no one has spotted them.

I fear that this sequel - rather than illuminating the unresolved mystery of the periquel - has actually shone a very hard spotlight directly on an unfillable plot hole and, as much, may be unwriteable.

 

[BillTre]

Migrations are a form of behavior. Behaviors can be fairly maleable some some changes are possible evolutionarially. However, wanting something to happen once in a while interspersed with a large number of "normal" events is different.

One could think of it this way:
Migrations can be conceived of as following a series of clues to get to the end site. If the normal migration path is disrupted in some way making the trip not possible or causing changes in the directing cues, then a migration could be occasionally go to an alternate site.
A timely severe hurricane or perhaps a disruption of the Gulf stream would be able to do this in some way.