Table 1 Comparison of morphological characters in Clypeaster sarawakensis nov. sp. with Clypeaster species present in (a) the Central Indo-Pacific fossil record, and (b) the modern Central Indo-Pacific and analysed in Mihaljević et al. (2011)
Morphological characters | Clypeaster sarawakensis F | Clypeaster annandalei M | Clypeaster blumenthali F | Clypeaster brevipetalus F | Clypeaster fervens M | Clypeaster humilis F M | Clypeaster latissimus F M | |
|---|---|---|---|---|---|---|---|---|
Marginal buttressing | Extent of marginal buttressing | Series of walls forming a wide buttressed zone | Series of walls forming a wide buttressed zone | NA | NA | Single internal wall around part or all of test* | Series of walls forming a wide buttressed zone | Series of walls forming a wide buttressed zone |
Ambulacral buttress organization | Bar(s) | Aligned pillars* | NA | NA | Aligned pillars* | Bar(s) | Bar(s) | |
Internal wall effectively forming a double wall with microcanal system | ?No | No | NA | NA | No | No | No | |
Radial bars projecting in from test margin along adradial sutures | Absent | Absent | NA | NA | Along just posterior interambulacrum (periproctal)* | Absent | Absent | |
Central buttresing | Central buttressing structures | Present | Present | NA | NA | Present | Present | Present |
Central buttressing of interambulacral zones | Infill of relatively fine pillars + bars in interradial zone | Dominated by large adradial bars/pillars bounding lower ends of petals* | NA | NA | Infill of relatively fine pillars + bars in interradial zone | Dominated by large adradial bars/pillars bounding lower ends of petals* | Infill of relatively fine pillars + bars in interradial zone | |
Central buttressing fused to form an almost continuous curtain enclosing petaloid area: | No | No | NA | NA | No | No | No | |
Central ambulacral zones within petals | Fine pillars only | No buttressing* | NA | NA | Fine pillars only | No buttressing* | Fine pillars only | |
Petals | Distance from distal end of petal III to ambitus vs. length of petal III: | ~ 0.46 (petals end midway to ambitus) | 0.35–0.65 | 0.35–0.65 | > 0.7—petals end far from ambitus* | 0.35–0.65 | 0.35–0.65 | 0.35– > 0.7 |
Petal III opened or closed - distance between inner pore-pairs vs. max broadness of inner 1-petals |  ~ 0.25 (relatively closed) | 0.76–0.95—widely open* | 0.76–0.95—widely open* | < 0.15—almost closed* | 0.76–0.95—widely open* | < 0.15—almost closed* | < 0.15—almost closed* | |
Petal II opened or closed -distance between inner pore-pairs vs. max broadness of inner petals |  ~ 0.25 (relatively closed) | 0.15–0.75 | 0.76–0.95* | < 0.15* | < 0.15* | < 0.15* | < 0.15* | |
Number of occluded plates in petal II | NA | 1–6 | ?1–6 | ?1–6 | >6 | >6 | >6 | |
Demi-plates in petals | Present | Present | ?Present | ?Present | Present | Present | Present | |
Test shape | Sunkeness of oral surface | Flat outer region with inturned test close to the peristome | Flat outer region with inturned test close to the peristome | Flat outer region with inturned test close to the peristome | NA | Test with broad adoral concavity* | Flat outer region with inturned test close to the peristome | Flat outer region with inturned test close to the peristome |
Angle of peristome to point of contact | 5°–10° | 0°* | 0°* | NA | > 10°* | 5°–10° | 0°* | |
Peripheral swollen rim | Present | Absent | Absent | Absent* | Absent* | Absent* | Absent* | |
Thickness of the test edge | Rounded | Thin/sharp* | Rounded | Thin/sharp* | Rounded | Thin/sharp* | Thin/sharp* | |
Food grooves | Food grooves | Present on oral surface only | Present on oral surface only | Present on oral surface only | Present on oral surface only | Present on oral surface only | Present on oral surface only | Present on oral surface only |
S/T ratio (distance of distal end of the food groove to ambitus vs. distance of peristome to ambitus) |  ~ 0.33 | < 0.35—food groove extends almost to ambitus | < 0.35—food groove extends almost to ambitus | NA | 0.4–0.7* | < 0.35—food groove extends almost to ambitus | < 0.35—food groove extends almost to ambitus | |
Combed area | Absent | Absent | Absent | NA | Absent | Absent | Absent | |
Tubercle differentiation along ambulacra | NA | Present, pores in distinct V-shaped region on each plate | Absent; pores scattered across plates | NA | Absent; pores scattered across plates | Present, pores in distinct V-shaped region on each plate | Present, pores in distinct V-shaped region on each plate | |
Periproct | Distance to ambitus from periproct/periproct length | ~ 0.64 | 0.8–1.5 | < 0.8 | NA | < 0.8 | < 0.8–1.5 | > 1.5* |
Situated between plates | NA | 4b and 3a | ?4b and 3a | NA | 4b and 4a | 4b and 4a | 4b and 4a | |
Situated | On oral surface | On oral surface | On oral surface | On oral surface | On oral surface | on oral surface | On oral surface | |
Tract of digestive system | Gut coiling | Runs anteriorly and loops back before reaching perradius of ambulacrum III | Runs anteriorly and loops back before reaching perradius of ambulacrum III | NA | NA | Comes out slightly left of centre and loops around front (crosses perradius of ambulacrum III)* | Comes out slightly left of centre and loops around front (crosses perradius of ambulacrum III)* | Runs anteriorly and loops back before reaching perradius of ambulacrum III |
Apical disc | Number of gonopores | 5 | 5 | 5 | 5 | 5 | 5 | 5 |
Lantern support structures | Lantern supports | Paired | Paired | ?Paired | ?Paired | Paired | Paired | Paired |
Interambulacral plates | Aboral surface composed of | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates |
Morphological characters | Clypeaster cf. malumbangensisF | Clypeaster miniaceus M | Clypeaster pateriformis M | Clypeaster phyllodes F | Clypeaster rarispinus M | Clypeaster reticulatus F M | Clypeaster saipanicus F | |
|---|---|---|---|---|---|---|---|---|
Marginal buttressing | Extent of marginal buttressing | NA | Series of walls forming a wide buttressed zone | Series of walls forming a wide buttressed zone | ?Series of walls forming a wide buttressed zone* | Series of walls forming a wide buttressed zone | Absent* | NA |
Ambulacral buttress organization | NA | Bar(s) | Bar(s) | NA | Bar(s) | – | NA | |
Internal wall effectively forming a double wall with microcanal system | NA | No | No | NA | No | No | NA | |
Radial bars projecting in from test margin along adradial sutures | NA | Along just posterior interambulacrum (periproctal)* | Absent | NA | Absent | Along just posterior interambulacrum (periproctal)* | NA | |
Central buttresing | Central buttressing structures | NA | Present | Present | NA | Present | Present | NA |
Central buttressing of interambulacral zones | NA | Dominated by large adradial bars/pillars bounding lower ends of petals* | Infill of relatively fine pillars + bars in interradial zone | NA | Infill of relatively fine pillars + bars in interradial zone | Dominated by large adradial bars/pillars bounding lower ends of petals* | NA | |
Central buttressing fused to form an almost continuous curtain enclosing petaloid area: | NA | No | No | NA | No | No | NA | |
Central ambulacral zones within petals | NA | No buttressing* | Fine pillars only | NA | Fine pillars only | No buttressing* | NA | |
Petals | Distance from distal end of petal III to ambitus vs. length of petal III: | > 0.7—petals end far from ambitus* | > 0.7—petals end far from ambitus* | > 0.7—Petals end far from ambitus* | > 0.7—Petals end far from ambitus* | > 0.7—Petals end far from ambitus* | 0.35–0.65 | 0.35–0.65 |
Petal III opened or closed - distance between inner pore-pairs vs. max broadness of inner 1-petals | < 0.15—Almost closed* | 0.76–0.95—Widely open* | < 0.15—Almost closed* | ? < 0.15—Almost closed | < 0.15—Almost closed* | < 0.15—Almost closed* | NA | |
Petal II opened or closed -distance between inner pore-pairs vs. max broadness of inner petals | < 0.15* | < 0.15* | < 0.15* | 0.15–0.75 | < 0.15—Almost closed* | < 0.15* | 0.15–0.75 | |
Number of occluded plates in petal II | ?1–6 | 1–6 | ?1–6 | ?1–6 | 1–6 | 1–6 | ?1–6 | |
Demi-plates in petals | Present | Present | Present | Present | Present | Present | ?Present | |
Test shape | Sunkeness of oral surface | NA | Flat outer region with inturned test close to the peristome | Flat outer region with inturned test close to the peristome | Flat outer region with inturned test close to the peristome | Flat outer region with inturned test close to the peristome | Test with broad adoral concavity* | Test with broad adoral concavity* |
Angle of peristome to point of contact | NA | 5°–10° | ?5°–10°* | 5°–10° | 0°* | 5°–10° | ? > 10°* | |
Peripheral swollen rim | Absent* | Absent* | Absent* | Absent* | Present | Present | Absent* | |
Thickness of the test edge | ?Rounded | Rounded* | ?Thin/sharp* | Rounded | Rounded | Rounded | Rounded | |
Food grooves | Food grooves | Present on oral surface only | Present on oral surface only | Present on oral surface only | Present on oral surface only | Present on oral surface only | Present on oral surface only | Present on oral surface only |
S/T ratio (distance of distal end of the food groove to ambitus vs. distance of peristome to ambitus) | NA | 0.4–0.7* | < 0.35—Food groove extends almost to ambitus | NA | < 0.35—Food groove extends almost to ambitus | > 0.7—Food groove confined to adoral region | ? > 0.7—Food groove confined to adoral region* | |
Combed area | NA | Absent | Absent | Absent | Absent | Absent | Absent | |
Tubercle differentiation along ambulacra | NA | Present, pores in distinct V-shaped region on each plate | ?Absent; pores scattered across plates | ?Absent; pores scattered across plates | Resent, pores in distinct V-shaped region on each plate | Absent; pores scattered across plates | ?Absent; pores scattered across plates | |
Periproct | Distance to ambitus from periproct/periproct length | NA | 0.8–1.5 | > 1.5* | 0.8–1.5 | <0.8 | 0.8–1.5 | 0.8–1.5* |
Situated between plates | NA | 5b and 4a | NA | NA | 4b and 3a | 4b and 3a | NA | |
Situated | On oral surface | On oral surface | On oral surface | On oral surface | On oral surface | On oral surface | On oral surface | |
Tract of digestive system | Gut coiling | NA | runs anteriorly and loops back before reaching perradius of ambulacrum III | runs anteriorly and loops back before reaching perradius of ambulacrum III | NA | Comes out slightly left of centre and loops around front (crosses perradius of ambulacrum III)* | Comes out slightly left of centre and loops around front (crosses perradius of ambulacrum III) | NA |
Apical disc | Number of gonopores | 5 | 5 | 5 | 5 | 5 | 5 | ?5 |
Lantern support structures | Lantern supports | ?Paired | Paired | ?Paired | ?Paired | Paired | Paired | ?Paired |
Interambulacral plates | Aboral surface composed of | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates | ambulacral and interambulacral columns of plates | Ambulacral and interambulacral columns of plates |