Stasis: 150 mya crab fossil is just like modern crab

_{Denyse O'Leary

March 11, 2015

News, stasis}

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Click to enlarge — living megalopa larva/Hsiu-Lin Chin

Arthropods (they of a hard outer-skeleton, like crustaceans, spiders, and insects) very often have larval phases that are completely different from the adults — such as caterpillars and butterflies. Allegedly, one of the reasons crabs have been so successful is that their larval life habits (diet, locomotion, etc.) are decoupled from their adult life habits.

Most ancient fossils display a suite of “primitive” features, consistent with their early evolution and allowing them to be distinguished from their modern descendants. But the fossil described in this paper, despite its age, possesses a very modern morphology, indistinguishable from many crab larvae living today. “It’s amazing, but if we did not know this was a 150-million-year-old fossil, we might think that it came from today’s ocean,” Dr. Martin said. “This came as quite a surprise to all of us.”

A friend, reading this, asks, wouldn’t these people be better off not to think about evolution at all? Maybe nature doesn’t care much about evolution and isn’t interested in fulfilling tenured profs’ predictions.

Anyway, abstract

True crabs (Brachyura) are the most successful group of decapod crustaceans. This success is most likely coupled to their life history, including two specialised larval forms, zoea and megalopa. The group is comparably young, starting to diversify only about 100 million years ago (mya), with a dramatic increase in species richness beginning approximately 50?mya. Early evolution of crabs is still very incompletely known. Here, we report a fossil crab larva, 150?mya, documented with up-to-date imaging techniques. It is only the second find of any fossil crab larva, but the first complete one, the first megalopa, and the oldest one (other fossil ca. 110?mya). Despite its age, the new fossil possesses a very modern morphology, being indistinguishable from many extant crab larvae. Hence, modern morphologies must have been present significantly earlier than formerly anticipated. We briefly discuss the impact of this find on our understanding of early crab evolution. – Joachim T. Haug, Joel W. Martin, Carolin Haug. A 150-million-year-old crab larva and its implications for the early rise of brachyuran crabs. Nature Communications, 2015; 6: 6417 DOI: 10.1038/ncomms7417 (paywall)

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Comments

This is no big deal. There are other examples of 100 million year fossils or there abouts that are similar or the same as present day fossils. Then there are widely new stuff all the time through the various geological eras. The real question is how the new stuff appeared. That is what the argument in evolutionary biology is all about, not whether new stuff appeared or old stuff remains or disappeared.jerry_{March 14, 2015
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CHartsil@2, the only thing that is really KNOWN from the fossil record is that there is a lot of non-evolution. That is only thing that CAN BE KNOWN with ANY certainty. Anything else is just speculation. This crab is another in the long list of examples that show no apparent evolution over many millions of years. Non-evolution, aka stasis, is the only thing that can be accurately measured against living examples. Everything else is just speculation based on imagination -- not much different than seeing shapes in an ink blot. There is no way to verify the claim for example that Tiktaalik was the ancestor to tetrapods. Neal Shubin can argue that this or that feature resembles this or that feature in modern tetrapods but beauty is in the eye of the beholder. This speculation is not true of living fossils. They can be laid down right next to the million year old fossil and compare, and over and over again these examples show non-evolution dominates. This is not what Darwin or any modern Darwin devotees expected or proposed. This is another nail in the coffin or Darwinism.Florabama_{March 12, 2015
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"We know your message means something very important on the planet of Self-Deception but here in on Terra, it’s just “mumbo jumbo”." >A creationist >Accusing someone else of self deception 40 keksCHartsil_{March 12, 2015
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Excellent thread with another great point about how practical evidence makes evolution unlikely. These crabs are found looking the same because the crab is now and in the past so common it would be found in the special cases of fossilization. in fact many creatures looking as they do today also were around when the fossils were made. They just lived in more segregated areas. Not common as crabs are. If evolution was turning bugs into buffalos but left the crab alone , remember all that time, then how so? No crabs evolved at all? How settled in ones place can one get??? The crabs are a clue that evolution never happened by even the reasoning of evolution. Of coarse these fossilized crabs are from the flood year. why are these crab researchers surprised? Way do they not predict these things? Are they now predicting this for other creatures? Surprise pretty soon is evidence of living in error.Robert Byers_{March 11, 2015
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CHartsil:
So if living fossils are evidence against evolution then non-living fossils are evidence for evolution. If not, then this is just a meaningless unfalsifiable assertion.
Earth to alien: We know your message means something very important on the planet of Self-Deception but here in on Terra, it's just "mumbo jumbo".Mapou_{March 11, 2015
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So if living fossils are evidence against evolution then non-living fossils are evidence for evolution. If not, then this is just a meaningless unfalsifiable assertion.
What is this? Kindergarten? SebestyenSebestyen_{March 11, 2015
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So if living fossils are evidence against evolution then non-living fossils are evidence for evolution. If not, then this is just a meaningless unfalsifiable assertion.CHartsil_{March 11, 2015
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I love this. Bacteria became human beings because the environment and food supply changed so much that all this just had to happen. But crabs show no evolutionary developments over the past 150 million years.
“It’s amazing, but if we did not know this was a 150-million-year-old fossil, we might think that it came from today’s ocean,” Dr. Martin said. “This came as quite a surprise to all of us.”
Dr. Martin and colleagues were surprised and found this to be "amazing". It's probably best if they don't say much more than that though, otherwise people might wonder why their theory didn't predict 150 million years of stasis. The abstract is informative:
Early evolution of crabs is still very incompletely known.
In other words, "we know a vast amount about it, but it's just very incomplete".
Despite its age, the new fossil possesses a very modern morphology, being indistinguishable from many extant crab larvae. Hence, modern morphologies must have been present significantly earlier than formerly anticipated.
Ok, they really worked on that one. They did not expect to find modern morphologies in a crab from 150mya. They found the modern morphologies. Therefore: "Modern morphologies must have been present significantly earlier than formerly anticipated." Yes, I think they might actually have a point there.
We briefly discuss the impact of this find on our understanding of early crab evolution.
I think the impact on later crab evolution can be discussed even more briefly: "Crabs may not have evolved at all over the last 150 million years". Good discussion!Silver Asiatic_{March 11, 2015
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