Bryozoan Hunt in Hawkes Bay, New Zealand

blogpost by Lee Hsiang Liow

Field paleontology is hard. Really hard. Literally. I spent much of my career as a shielded desk- and library-bound paleobiologist. In the last three years, however, I daringly put a serious field component into my research. This is in part because I was shown one of the most bryozoan-rich sedimentological sequences in the world when I was introduced to bryozoology, namely the Wanganui basin Pleistocene outcrops. Wanganui’s beautiful cliffs oozes bryozoans and their competitive interactions in endless volume. But Wanganui only presents about 2.3 million years of evolutionary history for its bryozoans.

And I am greedy. 2.3 million years are not enough, neither is stunning Wanganui. Having heard about limestones and shellbeds in Hawkes Bay of New Zealand that may offer a deeper view into the evolutionary history of New Zealand bryozoans, I summoned the help of GNS geologists (James Crampton, Alan Beu, Kyle Brand and Tom Womack) and my bryozoology colleagues (Dennis Gordon and his Ph.D student Carolann Schack) from NIWA, Wellington, to venture into the Pleistocene and Pliocene of Hawkes Bay. I was to figure out, in a week, if Hawkes Bay was an area that we could mine for fossil bryozoans in order to study their morphology, life history and evolution.

beach.png
Pleistocene marine outcrops in Hawkes Bay. Mostly limestone consisting of molluscs.

Hawkes Bay, New Zealand. It is famous for its wines, but it is also a mind-boggling spread of farmland and rural areas that also offers outcrops on dangerously windy, narrow roads, with frightening names such as “Devil’s Elbow” and immense lime quarries. The hard and cemented limestones were nothing like those in Wanganui and outcrop after outcrop only yielded “melted” bryozoans, “upside-down” bryozoans, cemented bryozoans or bryozoan traces and etchings. In other words, they were there, but they cannot be used for my purposes. There were also live-demonstrations that “detection probability” is a really dirty term in paleontology. I took this photo of Heteropora neozelanica on a fallen block in the field to document the new record of this bryozoan in the Tangoio Limestone (1.8 million years old).

Heteropora
Spot the inside down “Y” shaped erect colony of Heteropora neozelanica (about 1 cm in length) in the bottom right of this photo, then pick out the rest of the bryozoans that we did not see in the field.

Six pairs of eyes, three of them belonging to bryozoologists, and three to paleontologists who were looking for bryozoans, looked at this rock. We all saw this specimen of H. neozelanica when Dennis Gordon pointed it out, but not one of us saw the 5-6 other bryozoans that are also on the outcrop. Shocking? Not. That’s the rarely directly modelled “detection probability” in paleontology for you.

Hardhats, not wine. I was not in Hawkes Bay for their wine but it turned out I was there, unexpectedly, for the hardhat. Quarries are often a haven for paleontologists hunting for small fossils because of their exposing and breaking up of sediments and subsequent natural weathering and erosion.

Webster's
From left to right: Victoria University of Wellington graduate student Carolann Schack, NIWA scientist Dennis Gordon, and Robert Webster at his Havelock North Lime Quarry.
Hatuma
From left to right: Clifford Topp of Hatuma Lime Company Ltd, Dennis Gordon and Lee Hsiang Liow (with a fossil in hand).

Quarry directors Clifford Topp and Robert Webster kindly allowed Dennis, Carolann and me to come onsite to pick through material. They also allowed us to tell them about the intriguing marine creatures, many species of are not only much older than our own species but also continue to be alive in the seas of New Zealand and further afield today, such as Steginoporella magnifica and Odontionella cyclops. It was truly awe-inspiring to realize that the massive quarries we drove through are made of encrusting bryozoans and their substrates (special apologies to malacologists) and tons of erect, habitat-forming bryozoans.

interactions
Three million year old bryozoan colonies encrusting an equally old shell fragment (about 2 cm across), preserving their competition for space on a small substrate.

Science is about asking questions and learning. I have emerged from a whirl wind tour of Hawkes Bay with new knowledge that can only be gained by being in the field. I have so many new questions. How many bryozoans alive in New Zealand today were also alive in the Pliocene of New Zealand (I saw a few with my own eyes, but how many?) Why are they alive and not the others? Is it their life-history? Is it bad luck? How much does a species evolve and does that evolution really aid in evolutionary success? Slowly, but surely, we will inch towards revealing more about the secret lives of bryozoans.

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