Large-field electron imaging and X-ray elemental mapping unveil the morphology, structure, and fractal features of a Cretaceous fossil at the centimeter scale.
We used here a scanning electron microscopy approach that detected backscattered electrons (BSEs) and X-rays (from ionization processes) along a large-field (LF) scan, applied on a Cretaceous fossil of a shrimp (area ∼280 mm(2)) from the Araripe Sedimentary Basin. High-definition LF images from BSEs and X-rays were essentially generated by assembling thousands of magnified images that covered the whole area of the fossil, thus unveiling morphological and compositional aspects at length scales from micrometers to centimeters. Morphological features of the shrimp such as pleopods, pereopods, and antennae located at near-surface layers (undetected by photography techniques) were unveiled in detail by LF BSE images and in calcium and phosphorus elemental maps (mineralized as hydroxyapatite). LF elemental maps for zinc and sulfur indicated a rare fossilization event observed for the first time in fossils from the Araripe Sedimentary Basin: the mineralization of zinc sulfide interfacing to hydroxyapatite in the fossil. Finally, a dimensional analysis of the phosphorus map led to an important finding: the existence of a fractal characteristic (D = 1.63) for the hydroxyapatite-matrix interface, a result of physical-geological events occurring with spatial scale invariance on the specimen, over millions of years.
Solid-Biological Interface Group (SolBIN), Departamento de Física, Universidade Federal do Ceará , P.O. Box 6030, 60455-900 Fortaleza, Ceará, Brazil.
Naiara C
NC
Oliveira
Universidade Federal do Cariri , Cidade Universitária, 63048-080 Juazeiro do Norte, Ceará, Brazil.
João H
JH
Silva
Olga A
OA
Barros
Allysson P
AP
Pinheiro
Sistematic Zoology Laboratory (LSZ), Pró-Reitoria de Pesquisa e Pós-Graduação, Universidade Sagrado Coração (USC) , 17011-160 Bauru, São Paulo, Brazil.
William
W
Santana
Antônio A F
AA
Saraiva
Odair P
OP
Ferreira
Paulo T C
PT
Freire
Solid-Biological Interface Group (SolBIN), Departamento de Física, Universidade Federal do Ceará , P.O. Box 6030, 60455-900 Fortaleza, Ceará, Brazil.
Amauri J
AJ
Paula
D000818:Animals; D033364:Decapoda / Q000033:anatomy & histology* / Q000737:chemistry; D017886:Durapatite / Q000032:analysis; D005580:Fossils / Q000033:anatomy & histology*; D008855:Microscopy, Electron, Scanning / Q000379:methods*; D010758:Phosphorus / Q000032:analysis; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D014965:X-Rays
D010758:Phosphorus; D017886:Durapatite