The Lagoon That Puzzled Paleontologists for 250 Years

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0:02 from Good Idea Creations for supporting PBS.

0:07 For almost 250 years, excavations in the limestone quaries of southern

0:12 Germany have slowly revealed a secret, the remains of hundreds of terasaurs.

0:18 Now, terasaurs usually don't fossilize well.

0:20 Their thin hollow bones were often too

0:22 delicate to survive intact in the fossil record.

0:25 So while they once ruled the skies,

0:27 these flying reptiles barely left a trace that they even

0:30 existed at all outside of just a few key fossil sites.

0:34 At the Smoff Information in Germany, though,

0:36 over 500 fossils of 15 terasaur species have been found,

0:41 beginning in 1784 with the very first terasaur ever described.

0:45 [music] They date back to the late

0:47 Jurassic period around 150 million years ago when

0:51 the region was a tropical archipelago dotted with shallow

0:54 lagoons encircled by reefs of coral and sponges.

0:58 These lagoons formed a terasaur fossil factory preserving many of them

1:03 in incredible detail right down to the membraned wings and toughs of fluff.

1:08 But the Smoff information might be hiding a dark secret.

1:12 One that's been massively distorting our view of who was living

1:15 and dying there and why they left so much evidence behind.

1:19 Because it turns out that this treasure trove of terasaur

1:22 fossils may only exist thanks to a literal perfect storm.

1:30 The sonhof information is what's known in the field

1:32 of paleontology as a loggereta or storage place.

1:36 It's a term that's used to describe

1:38 fossil sites that have exceptional preservation.

1:41 Each one is kind of like a geological

1:42 miracle because fossilization is usually incredibly rare.

1:47 So, Logger Stetton represent a lucky few places where the right conditions came

1:51 together to fossilize species in large numbers or in amazing detail or both.

1:57 There often our best windows into ancient life.

2:00 But these amazing sites can in some ways be a bit of a curse

2:05 because what life those windows are showing us might be massively deceptive.

2:09 Take the Libria tarpits for example, a loggereta in Los Angeles.

2:13 Around 90% of the ancient mammals recovered from the tarpits are carnivores,

2:18 including thousands of direwolves and saber-tooth cats.

2:21 So should we assume that predators were [music]

2:24 actually 90% of the mammals on the landscape?

2:27 No, because that would be very weird.

2:30 Carnivores are often the rare ones in an ecosystem by a landslide.

2:34 Instead, it turns out that the tar pits are inherently biased toward them.

2:38 As herbivores got stuck in the tar and became exhausted,

2:42 predators flock there in search of an easy meal,

2:45 only to themselves become stuck in even greater numbers.

2:48 In other words, the fossil record of who died in a place

2:52 isn't always a perfect reflection of who lived in a place.

2:56 And until we really understand how and why a fossil site formed,

3:00 it's hard to trust it.

3:01 So paleontologists are constantly asking,

3:04 does a site accurately reflect the ecosystem that existed there?

3:09 Or is there bias involved in who fossilized and who [music] didn't?

3:13 Unlike Labraa though, other logger, including Salhoffen,

3:17 haven't revealed their specific biases so easily.

3:20 And Son Hoffen is especially strange,

3:22 not just because it's so unusually rich in detailed complete terasaur fossils,

3:27 but also because of the kinds of terasaurs we see there.

3:30 Normally, you'd expect bigger individuals and species

3:34 with more robust skeletons to fossilize better,

3:37 especially in fragile groups like terasaurs.

3:39 And in the few other good terasaur fossil sites we do have elsewhere,

3:43 that's pretty much what we see.

3:44 More larger, older specimens and fewer, smaller, younger ones.

3:48 But the Sonhof and Terasaur seem to skew the opposite way.

3:53 There are many wellpreserved small terasaurs, including lots of juveniles,

3:56 and only very rarely do we see some fragmentaryary evidence

4:00 [music] of anything reaching or exceeding 2 m in wingspan.

4:04 So for a long time, many scientists simply assume that this was

4:07 just a reflection of the terasaur community that lived there.

4:10 It seemed like these lagoon ecosystems were

4:13 a hot spot for diverse species of small terasaurs

4:16 and their [music] young and larger species were

4:19 rare both here and possibly in the Jurassic overall.

4:22 If you take the Sonhof and Terasaur fossils at face [music] value,

4:26 then that is what they suggest.

4:28 But in 2025, [music] a team of researchers

4:31 fully turned this assumption on its head,

4:33 saying that what we see at Sonhofen isn't actually

4:36 a typical snapshot of the species that live there.

4:39 Instead, it's a massively biased collection of terasaurs

4:43 brought together mainly by one shared factor.

4:46 They fell victim to catastrophic storms.

4:49 But how can the fossil record capture ancient

4:51 gusts of winds that blew 150 million years ago?

4:56 Well, the researchers discovered some intriguing evidence in two

5:00 tiny sonhoffen terasaurs [music] named Lucky and Lucky 2.

5:04 They belong to a small species called pterodactylus antiquis known

5:08 to have wingspans reaching only about a meter when fully grown.

5:11 And because lucky and lucky 2 are just weeks old at most,

5:15 their wingspans measure under 22 cm, [music] making them some of the smallest

5:20 terasaurs known from the entire fossil record.

5:23 By examining them under UV light, the researchers found that these two

5:27 terasaur babies have almost identical injuries.

5:30 Both had clean and slanted wing fractures.

5:33 in Ly's left humorous and in Lucky 2's right.

5:36 And the injuries don't seem to have been

5:38 caused by attacks from predators or collisions with objects,

5:42 both of which would have left other forms of damage as well.

5:45 Instead, they seem to be the result of powerful twisting

5:48 forces that strained and snapped their fragile wings during flight.

5:52 And they're eerily similar to injuries seen in the juveniles

5:55 of modern flyers like birds and bats during strong storm winds.

5:59 Beyond Dooming Lucky and Lucky Too,

6:02 the researchers argued that most of the Sonhof

6:04 and Terasaurs were probably also storm victims.

6:08 See, while none of the others have the same injuries,

6:11 we wouldn't necessarily expect them to.

6:14 Because when groups of modern birds are killed by storms,

6:16 we only see widespread injuries when these events happen over land.

6:20 [music] For example,

6:21 as the birds are flung into trees or rocks or fall to the ground.

6:25 But when deadly storms happen over marine environments,

6:28 only a small proportion die with visible skeletal injuries to tell the tale.

6:33 Most simply become exhausted and [music] drown.

6:36 So the tiny identical fractures of Lucky and Lucky Too may be rare evidence

6:41 of much larger mass mortality events that killed

6:44 hundreds or even thousands of terasaurs each time.

6:47 Now, if catastrophic storms were responsible for the terasaurs at Sonhoffen,

6:52 that may explain many of the strange things about fossils here,

6:56 including the fact that this loggereta even exists.

6:59 The storms didn't just kill these terasaurs.

7:02 They also brought with them the ideal

7:04 conditions to preserve their corpses before

7:06 they could be torn [music] apart by scavengers or decay and crumble away.

7:10 When dead terasaurs sank to the bottom of the lagoon floor,

7:14 they were rapidly buried in mud flows stirred up by the powerful wind and waves.

7:18 [music] And that rapid burial in fine

7:20 sediment almost immediately after death is probably

7:23 the main reason that so many incredible

7:26 terasaur fossils form there in the first place.

7:28 But it also potentially explains why the terasaur fossils

7:31 there are dominated by small and young individuals, too.

7:34 For one, bigger, older terasaurs would have been

7:38 able to escape or ride out the storms.

7:40 And even for those that were killed, their larger and more buoyant bodies would

7:44 generally float on the surface of the water.

7:46 Being on the surface long enough would have

7:48 increased their chances of being scavenged or of decomposing,

7:52 eventually falling to the lagoon floor in the form of isolated fragments.

7:56 [music] Which is probably why we have no

7:58 complete and wellpreserved evidence of large terasaur from Salhoffen.

8:02 Not because they weren't around,

8:04 but because they just didn't have the same chance to settle

8:07 intact and become rapidly buried [music] that the smaller terasaurs did.

8:12 What's more, the Sonhof and Terasaurs were probably not even a single community.

8:16 They may have [music] died together there,

8:18 but that doesn't mean that they lived together there.

8:21 Instead, the storms turned the site into a death trap.

8:25 Strong winds swept up diverse species from distant habitats across

8:29 the island chain and flung them out over the lagoons.

8:33 This gave the impression of a single coexisting

8:35 community of over 15 distinct species in this ecosystem.

8:39 But it's actually a jumble of individuals that just

8:42 happened to be caught up in the same catastrophes.

8:44 Many of whom weren't native to the lagoons at all.

8:47 Sonhoffen may be one of our single richest

8:50 and most influential sources of information on terasaurs ever found,

8:54 [music] but almost nothing about it is exactly as it seems.

8:58 And it points to a bigger kind of ironic problem

9:01 in paleontology known in the field as the loggera effect.

9:05 [music] The fewer fossils and fossil sites we have for an extinct group,

9:09 the more misleading the ones we do have can be.

9:13 Without a good frame of reference, it's not always clear if they're giving

9:16 us a typical unbiased glimpse into deep time.

9:19 Maybe what we're seeing has been distorted

9:21 by forces we don't even realize were involved.

9:24 And for terasaurs in particular, whose fossils are so rare,

9:28 the loggeretta effect clouds basic aspects of their ecology

9:32 and evolution more than almost any other ancient vertebrates.

9:36 From their diversity to their sizes to how and where they lived and died.

9:41 And if it wasn't for the unfortunate luckies,

9:43 our understanding of terasaurs might have been forever blown off course.

9:51 We'd like to thank Hungry Minds Publishing for supporting PBS.

9:55 [music] Hungry Minds is the international creative group of artists,

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10:52 [music] Terosaurs may be well known for their domination

10:57 of the skies in the Mesazoic era,

10:59 but they didn't live their entire lives in the air.

11:02 So, how did we figure this out?

11:04 And what were they like when they finally came down?

11:06 [music] Find out in our episode, When Terasaurs Walked.

11:10 And thanks to this month's exceptional eontologists, Addie,

11:14 Annie and Eric Higgins, Carl Wolfold, Jackie Scott Rston,

11:17 Jake Hart, John Davidson Ing, Juan M, Melanie Lamb,

11:21 Carnival, Nico Robin, Rafael Hos, Tony Dy, and Steve.

11:26 Become an Ionianite at patreon.com/eons and you can get fun perks

11:31 like a monthly digital puzzle of paleo art commissioned by Eons.

11:34 And as always, thanks for joining me in the Annie and Eric Higgins studio.

11:38 Subscribe at youtube.com/eons for more journeys in the Jurassic.

11:51 So, should we assume that predators were

11:54 actually 90% of the mammals on the landscape?

11:56 I feel like I ate the word [music] actually, so we're just going to come back.