Every single fossil in this record — all 276 of them — came out of the sea. But the honest answer here is mostly about what our sources cannot tell you. For the two oldest ages on this page, 200 and 250 million years ago, the plate model has no plate for this crust that far back, so it cannot say where this ground was at all. For the two after that there is rock here, but our rock database holds no environment for it: it was changed by heat and pressure into schist, which makes its original setting a harder question rather than an unanswerable one. So this page has three kinds of "no answer" in it, and telling them apart is the interesting part.
Five ages in the past of this place, each one a window rather than a day. Each says which witness spoke — and where our evidence cannot answer yet, it says that too.
“Ma” means millions of years ago. The dashed mark means our sources have nothing for that age — which is a finding, not a fault.
No place, no memory, one voice
No place — 200 and 250 million years ago
The plate model cannot place this ground at 250 million years ago at all — in its own words, “the static polygon containing this point is valid from 150 Ma to the distant future; the model cannot place this crust at 250 Ma”.
No memory — 100 million years ago
The one rock unit the region keeps from 100 million years ago is the Catalina Schist. It is metamorphic rock, and the rock database we use holds no environment for it — so our sources cannot answer the land-or-sea question here, even though the rock itself is far from a blank.
One voice — 66 million years ago
69 fossils dug up near Los Angeles have an age range covering 66 million years ago: 69 from the sea, 0 from land. The closest of them was found about 25 km away — near the city, never under it.
Continents are assembled over time, piece by piece, and a plate model only knows about a piece once it has arrived. That is one way to read a refusal like this one. Our data can say the model has no position for this ground and can quote its reason; it cannot show you the journey, so this page does not draw one.
Rock can also be changed after it forms — heated and squeezed until its original layers, and the evidence of where they formed, are rewritten. Geologists read schist that way. Our data says only what this rock is made of and that its environment record is empty, so that is where this page stops.
Travel back in time
Two of the five rows below say the model cannot place this ground at all. That is not the page giving up — it is the model being honest about a piece of crust that had not yet arrived.
250
million years agojump to the evidenceThe plate model cannot place this ground at 250 million years ago at all — in its own words, “the static polygon containing this point is valid from 150 Ma to the distant future; the model cannot place this crust at 250 Ma”.
200
million years agojump to the evidenceThe plate model cannot place this ground at 200 million years ago at all — in its own words, “the static polygon containing this point is valid from 150 Ma to the distant future; the model cannot place this crust at 200 Ma”.
150
million years agojump to the evidence150 million years ago, the plate model puts this ground about 25° north of the equator. Published models disagree by about 3.7° of latitude here — a few hundred kilometres — so it is one model's answer, not a photograph.
100
million years agojump to the evidence100 million years ago, the plate model puts this ground about 37° north of the equator. Published models agree more closely here, within about 2.1° of latitude, but it is still one model's answer rather than a photograph.
66
million years agojump to the evidence66 million years ago, the plate model puts this ground about 40° north of the equator. Published models agree more closely here, within about 0.4° of latitude, but it is still one model's answer rather than a photograph.
What was the water doing?
Five ages, oldest first. Each one has two kinds of witness — the rock of the wider region, and the fossils dug up near the city — and they are kept apart on purpose, because they are answers to different questions.
Each age here is a marker on the timeline, not a single day. The evidence that belongs to it comes with an age range of its own that overlaps the marker — so it can tell you what this stretch of time was like, and never what was happening on one exact date.
The model cannot place this ground
Around 250 million years ago
The plate model cannot place this ground at 250 million years ago at all — in its own words, “the static polygon containing this point is valid from 150 Ma to the distant future; the model cannot place this crust at 250 Ma”.
An open question
Neither of the evidence sources we use can answer this one: our regional rock record holds no unit for 250 million years ago at this point, and no fossil dug up nearby covers that age either. That is a real gap in the evidence, not a gap in the past — and saying so is more useful than guessing.
The model cannot place this ground
Around 200 million years ago
The plate model cannot place this ground at 200 million years ago at all — in its own words, “the static polygon containing this point is valid from 150 Ma to the distant future; the model cannot place this crust at 200 Ma”.
An open question
Neither of the evidence sources we use can answer this one: our regional rock record holds no unit for 200 million years ago at this point, and no fossil dug up nearby covers that age either. That is a real gap in the evidence, not a gap in the past — and saying so is more useful than guessing.
Only the fossils speak
Around 150 million years ago
150 million years ago, the plate model puts this ground about 25° north of the equator. Published models disagree by about 3.7° of latitude here — a few hundred kilometres — so it is one model's answer, not a photograph.
The rock of the region
The region does have rock from 150 million years ago, but our copy of the rock record holds no environment for it, so this source cannot answer the question — which is not the same as the rock having nothing to say.
The fossils dug up nearby
One fossil dug up near Los Angeles has an age range covering 150 million years ago: 1 from the sea, 0 from land. It was found about 24 km away — near the city, never under it.
Only the fossils speak
Around 100 million years ago
100 million years ago, the plate model puts this ground about 37° north of the equator. Published models agree more closely here, within about 2.1° of latitude, but it is still one model's answer rather than a photograph.
The rock of the region
The region does have rock from 100 million years ago, but our copy of the rock record holds no environment for it, so this source cannot answer the question — which is not the same as the rock having nothing to say.
The fossils dug up nearby
69 fossils dug up near Los Angeles have an age range covering 100 million years ago: 69 from the sea, 0 from land. The closest of them was found about 25 km away — near the city, never under it.
Only the fossils speak
Around 66 million years ago
66 million years ago, the plate model puts this ground about 40° north of the equator. Published models agree more closely here, within about 0.4° of latitude, but it is still one model's answer rather than a photograph.
The rock of the region
No rock layer from 66 million years ago survives in the regional record here, so the rock has nothing to say about this age.
The fossils dug up nearby
69 fossils dug up near Los Angeles have an age range covering 66 million years ago: 69 from the sea, 0 from land. The closest of them was found about 25 km away — near the city, never under it.
What was dug up nearby?
Every fossil below was found somewhere near Los Angeles, never under it, so each one carries the distance to where it was actually dug up. Note the dates carefully: most of these fossils are from around an age rather than from it, and the page says which is which. Anything younger than 66 million years — however famous — is outside this record's window and is not here.
Around 66 million years ago
A Squalicorax kaupi — its group, Chondrichthyes, is the sharks, rays and their relatives, whose skeletons are made of cartilage rather than bone — from around this time (its own age range is 72.2–83.6 million years) was dug up about 43 km from here, in the Chatsworth, Los Angeles County.
A Baculites — its group, Cephalopoda, is the group containing squid, octopuses, cuttlefish, nautiluses and extinct relatives such as the coiled ammonites — from around this time (its own age range is 72.2–83.6 million years) was dug up about 29 km from here, in the Tuna Canyon, Los Angeles County.
An Amphiura lymani — its group, Ophiuroidea, is the brittle stars, which are starfish relatives with long, slender, flexible arms — from around this time (its own age range is 72.2–83.6 million years) was dug up about 44 km from here, in the Chatsworth, Ventura County.
A Scutella — its group, Echinoidea, is the group containing sea urchins and sand dollars — spiny relatives of starfish — from around this time (its own age range is 72.2–83.6 million years) was dug up about 44 km from here, in the Chatsworth, Ventura County.
A Cymbophora triangulata — its group, Bivalvia, is the two-shelled animals, like clams, oysters and mussels — from around this time (its own age range is 72.2–83.6 million years) was dug up about 25 km from here, in Los Angeles County.
An Eupachydiscus — its group, Cephalopoda, is the group containing squid, octopuses, cuttlefish, nautiluses and extinct relatives such as the coiled ammonites — from around this time (its own age range is 72.2–83.6 million years) was dug up about 29 km from here, in Los Angeles County.
An Eutrephoceras — its group, Cephalopoda, is the group containing squid, octopuses, cuttlefish, nautiluses and extinct relatives such as the coiled ammonites — from around this time (its own age range is 72.2–83.6 million years) was dug up about 29 km from here, in the Tuna Canyon, Los Angeles County.
Around 100 million years ago
A Baculites — its group, Cephalopoda, is the group containing squid, octopuses, cuttlefish, nautiluses and extinct relatives such as the coiled ammonites — from 100 million years ago was dug up about 30 km from here, in the Tuna Canyon, Los Angeles County.
A Metaplacenticeras sanctaemonicae — its group, Cephalopoda, is the group containing squid, octopuses, cuttlefish, nautiluses and extinct relatives such as the coiled ammonites — from 100 million years ago was dug up about 25 km from here, in the Tuna Canyon, Los Angeles County.
A Turritella chicoensis — its group, Gastropoda, is snails, slugs and their relatives; many carry a single shell, while others have a reduced shell or none at all — from 100 million years ago was dug up about 25 km from here, in the Tuna Canyon, Los Angeles County.
A Lispodesthes rotundatus — its group, Gastropoda, is snails, slugs and their relatives; many carry a single shell, while others have a reduced shell or none at all — from 100 million years ago was dug up about 25 km from here, in the Tuna Canyon, Los Angeles County.
Around 150 million years ago
A Buchia concentrica — its group, Bivalvia, is the two-shelled animals, like clams, oysters and mussels — from 150 million years ago was dug up about 24 km from here, in the Santa Monica Slate, Los Angeles County.
We show these places to the nearest few kilometres rather than pinning them exactly. The scientists who recorded them know the spot far better than that — the full record is one click away in the Paleobiology Database, and it is free for anyone to read. We round them here because a map made for children is not a map for digging things up, not because anything is being hidden.
What changed?
Across the three ages the model can place this ground, it carries it from about 25° north to about 40° north. For the two ages before that the model has no plate for this crust at all, so it carries it nowhere — and that absence is the biggest change on this page.
The rock at the surface today is all young by comparison. The geological map of this exact point returns Cenozoic sedimentary rocks (Cenozoic), Quaternary sedimentary (Cenozoic), Quaternary alluvium and marine deposits (Cenozoic), Alluvial-fan deposits (Holocene).
How this crust travelled, or how the basin beneath the city formed, is not something our datasets answer — so this page does not say.
Try it yourself
Sharks, ammonites and sea urchins were dug up within a few dozen kilometres of this city, and every one of them lived in water. Water like it is still going round the cycle. Work out how much of your next glass has been through a dinosaur.
Every one of the 276 fossils in this record is a sea animal. Not one is from land.
At 200 and 250 million years ago the plate model refuses to place this ground, and it says why in its own words.
At 100 and 150 million years ago there IS a rock here, and our record holds no environment for it — while at 66 and 200 and 250 million years ago our regional record holds no rock of that age at all.
This page has three kinds of “no answer”: no rock in our record at all, rock our database holds no environment for, and a model that cannot reach back this far. Which is which — and what could a scientist go and look for to fix each one?
How sure are we?
Column facts describe an area of thousands to tens of thousands of km², centred tens of kilometres from the town coordinate. They are claims about a region, never about the rock beneath the town.
Fossil facts are a bounding-box sample around the town, each with its own distance from it; a fossil is never "here". The absence of fossils is not evidence of the absence of life — only of the absence of a recorded, published dig in this box.
Positions are model outputs, not observations. Independent plate models disagree by hundreds of kilometres at these ages, and that spread is the honest size of the uncertainty.
The land/sea question is answered only by the regional rock and the local fossils, separately, and never by the reconstruction — which says where this ground was and cannot say whether it was wet. There is deliberately no single field holding a one-word answer, because answering in one word would require merging a regional claim with a local one (CLAUDE.md rule 5). The nearby fossils are reported as a census of what has been found — which kinds are present, and how many of each — and never counted into a verdict: occurrence records are not statistically equivalent observations, so a plurality of them cannot establish an environment (science review, 2026-08-30).
Fossils are binned to their nearest slice age by age-range midpoint, with boundaries at the inter-slice midpoints 83, 125, 175 and 225 Ma. Those boundaries are an editorial choice, not a published stratigraphic scheme; a reviewer may prefer stage boundaries. Every occurrence keeps its own age range so the choice can be re-examined.
Sources
Macrostrat — the rock of the regionRead from version 2.3.9 of its data service on 27 August 2026.Peters, S.E. et al. Macrostrat: a platform for geological data integration and deep-time research. https://macrostrat.org, accessed on (date)Palaeogeography: Wright, N., Zahirovic, S., Müller, R. D., and Seton, M. Towards community-driven paleogeographic reconstructions: integrating open-access paleogeographic and paleobiology data with plate tectonics. Biogeosciences 10:1529-1541
The Paleobiology Database — the fossils dug up nearbyPBDB publishes no dataset version string; the data-service path (data1.2) and the datainfo access_time bound this claim.Fossil occurrence data from the Paleobiology Database (https://paleobiodb.org), released under CC0 1.0.Palaeo-coordinate cross-check (Paleobiology Database `pgm=gplates`): Wright et. al., 2013; Towards community-driven paleogeographic reconstructions.Palaeo-coordinate cross-check (Paleobiology Database `pgm=scotese`): Scotese, C.R., 2021. An Atlas of Paleogeographic Maps: The Seas Come In and the Seas Go Out, Annual Reviews of Earth and Planetary Sciences, v. 49, p. 669-718.Palaeo-coordinate cross-check (Paleobiology Database `pgm=seton`): Seton et. al., 2012; Global continental and ocean basin reconstructions since 200 Ma.
The EarthByte plate model — where this ground used to beMULLER2019 version 3.0, run with pyGPlates 1.0.0, licensed CC BY 4.0.GPlates: Müller, R. D., Cannon, J., Qin, X., Watson, R. J., Gurnis, M., Williams, S., Pfaffelmoser, T., Seton, M., Russell, S. H. J., Zahirovic S. (2018). GPlates: Building a virtual Earth through deep time. Geochemistry, Geophysics, Geosystems, 19, 2243-2261. https://doi.org/10.1029/2018GC007584Reconstructions computed with the GPlates Web Service (EarthByte Group, The University of Sydney).Plate model: Müller, R. D., Zahirovic, S., Williams, S. E., Cannon, J., Seton, M., Bower, D. J., Tetley, M. G., Heine, C., Le Breton, E., Liu, S., Russell, S. H. J., Yang, T., Leonard, J., and Gurnis, M. (2019), A global plate model including lithospheric deformation along major rifts and orogens since the Triassic. Tectonics, vol. 38, https://doi.org/10.1029/2018TC005462. Licensed CC BY 4.0.Plate model: Zahirovic, S., Eleish, A., Doss, S., Pall, J., Cannon, J., Pistone, M., Tetley, M. G., Young, A., & Fox, P. (2022). Subduction kinematics and carbonate platform interactions. Geoscience Data Journal, 9(2), p.371-383. Licensed CC BY 4.0.Coastline and static-polygon data by the EarthByte Group, licensed CC BY 3.0 Unported.
This record was assembled on from the datasets above. The ancient positions are reconstructions from a published plate model, not observations.
